Review and Synthesis: Putting It All Together
21 Exploring Human Biology with Fresh Eyes
Review of the Themes of Human Biology
When considering the structure and function of the human body, we discussed each organ system discretely. Why is it insufficient to only study discrete systems and functions of the body? Keep this question in mind as you review the themes of human biology.The body is more than the sum of its parts. It needs to maintain homeostasis throughout the network of systems to perform even the most basic functions of life.
Structure and Function
Learning Objectives:
- Explore the Big Ideas of Human Biology by examining connections between systems.
- Identify examples of structure and function in anatomy.
- Predict dysfunctions associated with altered anatomical structures.
As you have seen, function relies completely upon structure and altered structure can greatly affect function. The following exercises take a look at one way this relationship plays out in the Urinary system.
The Bladder
Within the urinary system, recall that the bladder is the organ that stores urine until elimination by urination. Since urination production is continuous and elimination occurs less frequently, the amount stored changes over time. We will examine how the anatomical structure of the bladder allows its physiological function.
To permit large volume changes, the lining of the urinary bladder has rugae, similar to the lining of the digestive system.
The detrusor muscle in the urinary bladder contains multiple layers of smooth muscle cells that align in different directions. These muscles are aligned in the long axis, as well as around the bladder as circles and as spirals. These smooth muscles are able to stretch and signal that voiding is necessary.
What are rugae?
- texture for absorption
- folds
- texture for secretion
- nerves
Hint: Ruga is latin for “crease” or “wrinkle”.
What is the purpose of these rugae?
- to receive signals such as hormones from the endocrine system
- to interface with other tissues of the lower abdomen
- to allow distension of the bladder to hold more liquid
- contains glands for secretion into the urine
Hint: In the stomach, rugae unfold after eating to hold the food for acid and enzymatic processing.
Why are the muscles oriented in different directions?
Gastric Bypass
Obesity is usually treated with altered lifestyle changes including altered diet and increased exercise. Occasionally, weight loss medication is used to supplement lifestyle changes. However, in severe cases, altering the stomach’s structure can also be used to reduce food intake. Two major types of surgery include adjustable gastric band (Lap-Band) and gastric bypass.
Gastric banding physically restricts the stomach from expanding. Without the band, an adult’s stomach can expand from 50 mL to hold about 1 liter of food, and can distend to hold as much as 4 liters. There are numerous structures which allow this distension function.
Less food can fit into a stomach with a gastric band, and individuals feel full sooner. With gastric bypass surgery, stapling the stomach reduces stomach volume. Also, a portion of the small intestine is bypassed.
Learn By Doing #2
How can the unmodified stomach expand?
- gastric pits expand and unfold
- sphincters allow stomach elongation
- the fundus expands into the esophagus
- smooth muscle cells relax outward
Hint: The stomach is permanently bounded on each end, so it can only expand outward.
In addition to the reduced stomach size, what other function does removing part of the small intestine have?
- reduced mixing with digestive fluids and nutrient adsorption
- altered water adsorption and reduced bloating
- removal of nerves that trigger hunger
- removal of bacteria
Hint: Consider the function of the duodenum.
Sickle Cell: Altered Red Blood Cell Shape
In sickle cell anemia, low oxygen conditions lead to an altered red blood cell shape and reduced elasticity. Stiffer red blood cells can lead to vessel occlusion and ultimately tissue damage.
Learn By Doing #3
Why do red blood cells need to expand elastically?
- They need to expand when oxygen enters the cells.
- Red blood cells bind to fibrin fibers to accentuate clots.
- Red blood cells bind to other cells in the vessels.
- They need to deform in order to fit through capillaries.
Hint: While flowing through the circulation, red blood cells regularly deform and regain their shape.
Levels of Organization: Electrical Conductivity and Cell Metabolism
Learning Objectives
- Identify how different anatomic size scales integrate for physiological function.
- Predict what occurs at length scales if there is dysfunction at another length scale.
As we’ve seen throughout this course, the human body is a complex, hierarchical system. We’ve studied each level separately and how each level builds to form, support and become a system. Let’s now take a closer look at how these levels of organizations integrate.
Electrical Conductivity in the Heart
We can only live for a few minutes without the heart beating. This event, which occurs millions of times in a lifetime, is a function of many length scales within the cardiac tissue of the heart.
Learn By Doing #4
What movement of what molecules are primarily responsible for electricity in the heart?
- Ions
- water
- DNA
- proteins
Hint: Although numerous macromolecules are involved in generating electricity in the heart, only one type of molecules moves.
What cells are responsible for electrical stimulation in the heart?
- pacesetter cells
- pacemaker cells
- cardiomyocytes
- endothelial cells
Hint: Although different cells within the heart conduct electricity, specialized cells initiate the electrical stimulation.
In what region of the heart is the electrical stimulation started?
- Bundle of His
- AV Node
- Purkinje fibers
- SA Node
Hint: Consider the region of the heart where the electricity originates not the conduction system.
What other organs produce electrical stimulation?
Oxygen for Cell Metabolism
Obtaining oxygen is important for metabolism in every cell throughout the body. The respiratory system is dedicated to this exchange with the environment. Coordination of respiratory and cardiovascular function allows uptake of oxygen by respiration, exchange to the cardiovascular system, and distribution of oxygen through the body by the cardiovascular system.
Learn By Doing #5
What molecule binds to oxygen for efficient transport throughout the body?
- heme
- water
- lipids
- surfactant
Hints: A majority of oxygen is transported by hemaglobin. Consider the functional unit of the macromolecule.
What cells transport oxygen throughout the body?
- immune cells
- endothelial cells
- lung epithelium
- red blood cells
Hint: The iron of the heme has a bright red color.
Where does exchange from the atmosphere to the body occur?
- nose
- heart
- alveoli
- trachea
Hints: Oxygen exchange in the lungs occurs at the high surface area terminal regions. Oxygen exchanges between the atmosphere and the red blood cells in the cardiovascular system in the lungs.
Levels of Organization: Sickle Cell and Obesity
Learning Objective
Sickle Cell’s Gene Mutation Across Length Scales
In sickle cell anemia, there is a mutation in gene for the β-globin protein, which is part of hemoglobin. The altered structure of β-globin causes an aggregation of the proteins. When these proteins aggregate, they distort the shape of the red blood cell and reduces red blood cell elasticity. The abnormal cells get stuck in capillaries, reducing blood flow to tissues and organs. Organ damage may result, permanently affecting body function. Thus, a seemingly tiny error in DNA causes significant changes in the body’s systems at higher levels.
Oxygen levels drastically affect the severity of sickle cell anemia. Low oxygen conditions, such as at high altitudes, promotes red blood cell sickling in individuals with the mutation that leads to sickle cell disease.
Learn By Doing #6
Match the length (or size) scale and the change occurring at that level to the descriptions in the table below.
Length Scales: tissue/organ/body level, environment, cell level, chemical level, population, molecular level
Changes: oxygen, low oxygen levels, occlusion (blockage), β-globin, red blood cells, genetic mutations found in certain groups
| Length Scale (from smallest to largest) | Change | Effect of Change at that Level |
| The ability to bind this substance is reduced. | ||
| This mutated protein is altered in how it binds oxygen. | ||
| These cells sickle in low oxygen conditions. | ||
| This leads to reduced oxygen for tissues and organs in the body. | ||
| Some conditions, such as those found at high altitudes, make the disease more severe. | ||
| This mutation provides resistance to infection with the malaria parasite. |
Obesity Followed Through the Levels of Organization
Obesity is caused by excessive food intake and reduced physical activity. Genetics and cultural surroundings can also play a part. Let’s examine how levels of organization all have contributing factors on obesity.
- Increased carbohydrates and lipid intake: at the molecular level, excessive food intake can lead to accumulation of fat and altered body chemistry.
- Decreased activity leads to reduced muscle mass: at the cellular and tissue level the inactivity of obesity is associated with decreased activity, muscle tone and muscle mass.
- Obesity is also strongly correlated with the local population demographics.
Learn By Doing #7
Which of the following isnota carbohydrate that could lead to obesity?
- glucose
- cellulose
- starch
- fructose
Hint: All of the choices are carbohydrates, but one cannot be processed for energy.
How is muscle mass lost?
- underutilized muscle fibers die
- underutilized muscle fibers shrink
- underutilized muscle fibers lie dormant and are not used
Hint: When muscles grow with exercise, they hypertrophy. Hypertrophy means that cells get bigger; cells do not divide to make more.
Which isnota strong contributing factor to the correlation of obesity with lower income individuals of inner cities of the United States?
- reduced air quality from vehicle emissions
- reduced access to nutritious foods versus high calorie, high fat foods
- reduced formal education on healthy habits
Hints: Obesity is related to numerous environmental issues including what people eat. Proper nutrition is related to food availability and picking the best of the option.
Homeostasis
Learning Objectives
- Define homeostasis, and identify specifics aspects of physiology involving homeostasis.
- Complete homeostasis loops associated with physiology.
pH Balance
The lungs and kidneys work together to regulate the hydrogen ion concentration (pH) of arterial blood. This pH must be kept within a narrow range (7.38 – 7.42). An increase in pH (alkalosis) or decrease in pH (acidosis) can result in profound effects within the body. For example, certain amino acids are sensitive to the pH in their environment. An unusual pH could result in conformational changes in proteins and subsequently a change in the proteins’ functions.
Learn By Doing #8
Which of the following changes would result in acidosis?
Hint: Consider the bicarbonate buffer system: CO2+ H2O ⇌ H2CO3⇌ HCO3–+ H+
- increase in blood carbon dioxide concentration
- Hyperventilation
- Decrease in cellular metabolism
- Decrease in blood carbon dioxide concentration
Which of the following factors would result in a blood pH disturbance?
- high fat diet
- severe diarrhea
- heavy exercise
- all of the above
Blood Glucose
Solute and water balance is maintained when solutes and water enter and exit the plasma at the same rate. When one material enters or exits the plasma faster than the other, a change in volume and/or composition occurs. The plasma concentrations of many substances are controlled by specific regulatory mechanisms.
Learn By Doing #9
When you eat a meal high in glucose, there is an increased absorption of glucose from the lumen of the gastrointestinal tract. This results in an increase in blood glucose. Why is such a disturbance in homeostasis transient?
Hint: Consider the function of the endocrine system when glucose levels increase.
- Glucose levels decrease following increased secretion of GH
- glucose levels decrease following increased secretion of insulin
- glucose levels decrease following increased secretion of glucagon
Exercise
Body muscles use the energy from ATP molecules to generate the force necessary to contract. A byproduct of this energy release is heat release. This results in an increase in body temperature during intensive exercise. The body compensates for extra heat by causing vasodilation of blood vessels near the skin and by causing sweat glands to release sweat.
Learn By Doing #10
What other compensatory effects would occur within the body during intensive exercise?
Hint: Exercise results in a greater demand for oxygen in the muscle tissues.
- increased breathing rate
- increased heart rate
- decreased heart rate
- both 1 and 2
Homeostasis Considerations and Sickle Cell Disease
Learning Objectives
- Complete homeostasis loops associated with physiology.
- Predict dysfunctions associated with misregulation of homeostasis.
Red Blood Cells in Sickle Cell Anemia
Sickle cell anemia can lead to reduced oxygen delivery to tissues. Also, reduced red blood cell elasticity can lead to cell rupture and anemia. Anaemia is measured by a reduction in iron. It can be caused by iron deficiency, insufficient red cell production or red blood cell dysfunction; in this case dysfunction. When red cells are sickled, they only have a lifespan of 10-20 days whereas normal red blood cells have a lifespan of >100 days.
If red blood cells are not able to be replenished and the patient becomes anemic then different regions of the body can be deprived of oxygen. The effects of anemia can be compounded by obstruction of blood vessels by sickled cells. When tissues do not have sufficient oxygen, cells die by apoptosis or necrosis. Apoptosis is programmed death, which is a natural part of remodeling: when tissues are remodeled cells invade or proliferate (divide) to perform a function and they are done, the undergo apoptosis. This type of cell death does not cause disruption to the cells surrounding the dying cell. Necrosis on the other hand triggers uncontrolled release of cell products into intracellular space which in turn initiates an inflammatory response in the surrounding tissue.
Necrosis is similar to a feed-forward loop. Following cell injury as a result of infection or trauma, cells die and release toxic materials from inside the cell (including enzymes and low pH from lysosomal compartments) and trigger invasion of immune cells. These chemicals and immune cells then affect surrounding cells causing necrosis in surrounding cells.
Learn By Doing #11
How would the body deal with reduced red blood cell lifespan to prevent anemia and maintain homeostasis?
Hint: In this case, the shortened lifespan of cells means fewer cells in circulation unless more can be produced.
- better usage of each red blood cell
- using other means of oxygen transport
- increased red blood cell production by increased hematopoiesis
- more iron per red blood cell
What type of loop is this ‘downward spiral effect’?
- Negative feed-back loop
- Positive feed-back loop
Hint: Negative feed-backs lead back to the set point and positive feed-back loops lead away from a set point.
Match the components of the feedback loop described above with their role in the feedback loop.
Components: further release of toxic materials, release of toxic materials, cell injury
- __________________ is the initiation event for the feedback loop.
- The stimulus is __________________.
- The effectors that make adjustments in this system are __________________.
Integration of Systems
Learning Objectives
- Identify examples of integrated systems.
- Predict how dysfunction observed in one organ system could reflect dysfunction in other systems.
Throughout the course, we considered organ systems as separate systems. However, since the body functions as a single unit, the physiology of organ systems cannot truly be understood in isolation of other systems. Here, we will consider pathological conditions which impact multiple organ systems. We will also highlight how a thorough knowledge of physiology will allow a proper diagnosis of a disease of one organ system caused by another.
Diabetes
A podiatrist sees unhealed sores on a patient’s feet. He inquires if the patient has noticed any problems with vision in the past few months. When the patient says that his eyes have been bad, the podiatrist refers the patient to an endocrine specialist to be checked for diabetes.
Learn By Doing #12
What do sores on the feet suggest about patient health?
Hint: Diabetes shows early effects in the urinary and immune system.
- Overgrowth of the epidermis
- poor circulation and reduced immune system
- muscular and skeletal dysfunction
- Excessive exercise caused by increased blood sugar
Lymphatic: Splenic Sequestration Crisis
One of the main functions of the sinuses of the spleen is to break open senescent (old) red blood cells for processing. In individuals with severe sickle cell anemia, the spleen can be affected and vessels become occluded. Splenic sequestration crises are painful enlargements of the spleen, which cause nausea and abdominal bloating. This condition can cause circulatory failure and be fatal if not treated. To avoid these complications, some patients have a splenectomy (removal of the spleen).
Learn By Doing #13
What other impacts would a removal of the spleen have?
Hint: The spleen is an organ of the lymphatic system.
- reduced urinary function
- reduced digestive function
- reduced immune function
- reduced endocrine function
Obesity Exercise
Now, let’s look at the condition of obesity in more depth. Below is an activity that provides several sections of content and questions that will help you recall, organize and apply what you have learned in this course to the comprehensive condition of obesity. Obesity is a condition that affects much of the body – both in ways we can and cannot see. Explore the following material to learn how obesity affects each system of the body.
Directions:Explore common changes that are a result of obesity by reviewing the information below. The numbers on the line drawing correspond to the influences of obesity on the numbered area of the body and are matched by paragraph numbers below.
1 Sleep Apnea and Shallow Breathing
Obesity can hinder respiratory function. With fat accumulation around the waste, the diaphragm muscle becomes distended. The diaphragm is the primary inspiratory muscle for respiration. If the diaphragm’s function is impeded, muscles in the upper chest and throat have more of the mechanical burden for breath.
Sleep apnea is a sleep disorder that presents itself with abnormal pauses in breathing (known as apneas) that can last anywhere from several seconds to a minute. The most common form of sleep apnea,obstructive sleep apnea, can be caused or exacerbated by obesity. The low muscle-tone and excessive amount of soft tissue in the throat area can cause breathing to be obstructed. This subsequently results in temporary episodes of an inability to breath.
2 Acid Reflux
Strong acids and enzymes (such as HCl and pepsin, respectively) are generated by the stomach to promote food digestion. The esophagus is protected by this gastric juice by the lower esophageal sphincter, which holds shut the barrier between the bottom of the esophagus and the top of the stomach. When stomach acid manages to make its way through a faulty lower esophageal sphincter and into the esophagus, it results in a condition known asacid reflux. This phenomenon is colloquially known as heartburn because of the burning sensation felt in the general area where the heart is located.
An adult stomach is designed to expand to allow the intake of food. However, when a person habitually takes in large meals, the stomach grows. In addition to stomach distension, the peritoneal cavity has can gain increased visceral fat. This generally occurs as a result of excess caloric intake.
3 Heart Strain
Obesity results in an increase in body fat and subsequently body mass. This forces the heart to work harder and exert greater force when pumping blood throughout the body. The increase in body fat also results in greater levels of cholesterol in the blood vessels. Blood vessel constriction further increases the strain on the heart. As the heart is forced to work harder and harder, it requires greater quantities of oxygen. Heart failure can result when lack of oxygen results in death of cardiac muscle. This is typically a result of impeded blood flow due to fat-clogged blood vessels.
4 Breast and/or Other Cancers. . .
Obesity has been found to be correlated with an increased risk of breast cancer. This is speculated to be a result of increased levels of estrogen in obese women. After menopause, the ovaries stop producing hormones, which puts the burden of estrogen production on fat tissue. Since obese women have greater amounts of fat tissue, their estrogen levels are higher. This subsequently results in more rapid growth of estrogen-responsive breast tumors.
Obesity is also associated with an increased risk of cancer in the esophagus, pancreas, kidneys, thyroid, gallbladder, endometrium, colon and rectum.
5 Skin Imbalance
Numerous complications in the integumentary system can arise as a result of obesity. For example, obesity can result in insulin resistance, which subsequently leads to larger concentrations of insulin circulating in the bloodstream. Excess insulin impacts the skin causing abnormal growth, referred to as hyperplasia. The hyperplasia can lead to a disease known as acanthosis nigricans, which presents itself as brown or black hyperpigmentation of the skin.
Increased strain on leg veins due to obesity can result in fluid retention and swelling (edema), superficial capillary rupture, and ulcers. The increased weight can also result in corns and calluses on the feet. Most of these conditions can be resolved weight loss.
6 Urinary Incontinence
Urinary incontinence is the inability to control urine flow. Obesity often presents itself with urinary incontinence because of increased weight in the midsection. This causes extra pressure that makes it more likely that the bladder will leak. This results in stress incontinence, or the tendency for the bladder to leak when performing everyday actions such as laughing or coughing. Obesity is also strongly correlated with diabetes, which can cause damage to the nerves that control bladder muscles.
7 Joint Strain
Joints are found at the location where two or more bones make contact. Their general purpose is to allow movement, and they also serve to provide mechanical support. Joints essentially carry the weight of our bodies. So, the more weight they are forced to carry, the greater the strain it places on the joints. Small changes in weight can have substantial effects on joint forces in the hips and knees. Research has shown that obese individuals are more likely to develop arthritis.
8 Poor Circulation
Calf muscles rely on a constant supply of fresh blood to the muscle tissues. In a healthy individual, this blood is returned back up to the body against gravity via a pumping system formed by the leg muscles. The main driving force for this pumping system is supplied by the calf muscles as they contract, which takes pressure off the veins, allowing blood to return to the upper body. As blood passes through these veins, one way valves found in the veins shut to prevent blood from returning to the feet. This used blood is subsequently displaced by the same volume of fresh blood.
Because obese individuals tend to lead a life of little movement and activity, the ability of their legs to contribute to circulation decreases substantially. This results in a disruption of the aforementioned cycle, and used blood remains in the lower legs. This causes water from lymph fluid to separate from the blood and fill spaces in tissues, resulting in edema.
Learn By Doing #14
Thinking about lung function, why would excess fat produce shallow breathing?
Hint: Sit up straight and take a deep breath. Now slouch and do the same. Do you notice a difference? If so, why?
- excess fat pushes down on the diaphragm, not allowing it to expand
- excess fat cells in the body require more oxygen. This increased demand makes breathing seem shallow.
- less fluid production leads to less blood available for oxygen transport
- alveoli become smaller, so less oxygen is transported throughout the body
Obesity hypoventilation syndrome is a condition caused by failure to breathe rapidly and/or deeply. How could this adversely affect the body?
Hint: Consider the gas exchange that occurs in the lungs.
- low blood carbon dioxide level
- slow heart rate
- low blood oxygen levels
- low blood glucose levels
Sleep apnea can disrupt regular sleep patterns. Given what you know about sleep patterns, what do you predict will be affected?
Hint: Imagine you have stayed up all night to write a term paper. How do you imagine yourself feeling the next day?
- mood
- alertness
- headaches
- both 1 and 2
- all of the above
Chronic acid reflux can result in mucosal damage, which can lead to gastroesophageal reflux disease (GERD). The risk of GERD is substantially greater in obese individuals. Which of these obesity-related factors would cause this condition or cause it to worsen?
Hint: GERD is typically caused by changes in the barrier separating the stomach and esophagus.
- Eating fatty foods
- The smooth muscle forming the upper esophageal sphincter degrades
- Putting excess pressure on the lower esophageal sphincter
- Esophageal lining becomes more sensitive
If an obese individual also smokes cigarettes, how could smoking potentially worsen heartburn?
Hint: Cigarettes contain nicotine, which can have numerous effects on the gastrointestinal system.
- Stomach acidity is increased
- Saliva production is decreased
- Lower esophageal sphincter function is impaired
- All of the above
How does fat from the diet enter the bloodstream?
Hint: Fats are non-polar and therefore hydrophobic.
- Packaged into lipoproteins
- Carried by Islet cells
- Enter the bloodstream directly
- Carried by red blood cells
Obesity results in a decrease in high density lipoproteins (HDL). How could this adversely affect an individual’s health?
Hint: HDLs are high in density and rich in protein.
- Increased risk of heart disease
- Increased risk of stroke
- Increased risk of diabetes
- Increased risk of cancer
- Both 1 and 2
- All of the above
Obesity is linked with greater resistance to insulin. How could this potentially result in a greater risk of breast cancer?
- Insulin can trigger the growth of breast cancer cells.
- Glucose in the bloodstream can trigger growth of breast cancer cells.
- Medications used to treat insulin resistance can trigger growth of breast cancer cells.
- All of the above
How does retained moisture result in skin rashes and other infections?
Hint: Consider the optimal growth conditions for foreign disease-causing agents.
- decrease in passive immunity
- decreased antibody production
- encourages microbial (bacteria and fungus) growth
- moisture kills neutrophils
When excess fat creates folds in the skin, what will happen to skin within the folds?
Hint: The formation of folds in the skin results in obstruction of sweat glands.
- large amounts of perspiration in this area
- formation of a tumor within the skin fold
- vitamin D deficiencies from lack of direct sunlight
- formation of a heat rash
What causes the symptoms of dehydration and thirst in individuals with higher blood glucose levels?
Hint: Consider the role of glucose in maintaining fluid/solute balance with the nephron.
- Free glucose inhibits cells from absorbing water.
- Cells require more water to produce glucagon.
- Glucose increases osmotic pressure of the urine.
- All of the above
Osteoarthritis can occur in individuals who engage in high risk sports as well as those who are sedentary but obese. Why is this?
Hint: Synovial fluid reduces friction between the cartilage of synovial joints during movement.
- increased synovial fluid from increased adrenaline production
- increased synovial fluid production from increased load and use
- both 1 and 2
Which of the following are not causes of poor circulation?
Hint: If blood vessels were to vasodilate, circulation would be unimpeded.
- Increased release of histamine
- Thrombus formation
- High cholesterol levels in blood vessels
- Arteriosclerosis
Correct. This would result in vasodilation and would result in unobstructed blood flow.
Did I Get This #1
Which of these factors is directly responsible for the high incidence of breast cancer in older, obese women?
Hint: The growth of many breast tumors is estrogen-responsive.
- Breast tissue becomes more sensitive to estrogen
- Buildup of fat tissue around the breast results in tumor formation
- Reduced number of hormonal receptors on breast tissue cells
- Large amounts of fat tissue produce lots of estrogen
How else can excess fat affect negatively affect the body?
Hint: Imagine you are forced to walk around for a day in clothing that adds an additional 50 pounds to your weight. How do you imagine this would affect your body?
- Back and spinal pain
- Pain in muscles of the upper chest and throat
- Arthritis in the joints
- All of the above
Which of the following conditions is not a potential result of obesity?
Hint: One of the following conditions is an autoimmune disorder that is unrelated to obesity.
- acanthosis nigricans
- cellulitis
- callus
- contact dermatitis
What is the link between obesity and insulin insensitivity in cells?
*
“Learn By Doing” and “Did I Get This?” Feedback
What are rugae?
- texture for absorption
Incorrect. The bladder does not have any absorption or secretion; it is only for containment. - folds
Correct. Rugae are found in the wall of the stomach as well as the wall of the bladder. - texture for secretion
Incorrect. The bladder does not have any absorption or secretion; it is only for containment. - nerves
Incorrect. There are nerves in the wall of the bladder to sense distension, but they are not called rugae.
What is the purpose of these rugae in the bladder?
- to receive signals such as hormones from the endocrine system
Incorrect. The rugae unfold based on mechanical distension not endocrine regulation. - to interface with other tissues of the lower abdomen
Incorrect. Interaction between the bladder and other organs of the lower abdomen occurs on the external face of the bladder. rugae are found primarily on the inside. - to allow distension of the bladder to hold more liquid
Correct. Rugae unfold to allow the bladder to expand, after elimination the rugae refold to reduce internal volume. - contains glands for secretion into the urine
Incorrect. Secretion occurs before the ureter and bladder.
Why are the muscles oriented in different directions?
Our Answer: No matter how the bladder distends – up, down or radially outward – the smooth muscles will always be able to sense the dilation.
Learn By Doing #2
How can the unmodified stomach expand?
- gastric pits expand and unfold
Incorrect. Rugae can expand outward, but the function of gastric pits is to secrete material. - sphincters allow stomach elongation
Incorrect. Sphincters keep food in the stomach, but they do not cause shape changes. - the fundus expands into the esophagus
Incorrect. The stomach distends outward but not into the esophagus or duodenum. - smooth muscle cells relax outward
Correct. Rugae smooth out to add some increased volume, and the walls also distend with smooth muscle cells.
In addition to the reduced stomach size, what other function does removing part of the small intestine have?
- reduced mixing with digestive fluids and nutrient adsorption
Correct. With less nutrient adsorption fewer carbohydrates and fats enter the body. - altered water adsorption and reduced bloating
Incorrect. Water is absorbed primarily in the large intestine. - removal of nerves that trigger hunger
Incorrect. The hormones and sensory nerves associated with eating are primarily in the stomach. - removal of bacteria
Incorrect. Native bacteria are found in the large intestine.
Learn By Doing #3
Why do red blood cells need to expand elastically?
- They need to expand when oxygen enters the cells.
Incorrect. Oxygen binding to hemoglobin at the nanoscale does not alter cell shape at the microscale. - Red blood cells bind to fibrin fibers to accentuate clots.
Incorrect. Red blood cells can interact with fibers, but they are not adhesive. platelets are. - Red blood cells bind to other cells in the vessels.
Incorrect. Unless there is a serious pathological issue (such as malaria infection) red blood cells are not adhesive to vessel walls. - They need to deform in order to fit through capillaries.
Hint: While flowing through the circulation, red blood cells regularly deform and regain their shape.
Correct. Red cells squeeze through capillaries and tight spaces in the capillary beds of the lungs, liver and spleen.
Learn By Doing #4
What movement of what molecules are primarily responsible for electricity in the heart?
- Ions
Correct. The movement of sodium and potassium across cell membranes generate an action potential. - water
Incorrect. Water moves throughout the cytosol but is not responsible for electrical conduction, ions are. - DNA
Incorrect. DNA has a charge, but since it is localized within the nucleus, it does not impact charge. - proteins
Incorrect. Ion channels, which are proteins, control movements of ions. They, themselves don’t move.
What cells are responsible for electrical stimulation in the heart?
- pacesetter cells
Incorrect. These are responsible for electrical conduction in smooth muscle cells. - pacemaker cells
Correct. The pacemaker cells are specialized cardiac muscle cells. - cardiomyocytes
Incorrect. Pacemaker cells are specialized cadiomyocytes, but are usually referred to by a special descriptor. - endothelial cells
Incorrect. These cells line blood vessels and the inside of the heart, but they do not have electrical function.
In what region of the heart is the electrical stimulation started?
- Bundle of His
Incorrect. The Bundle of His anatomically connects the AV node with thee purkinje fibers, but electricity is not stimulated there. - AV Node
Incorrect. The AV node coordinates the electrical conductivity, but electricity is not stimulated there. - Purkinje fibers
Incorrect. These fibers transmit electricity through the ventricles, but electricity is not stimulated there. - SA Node
Correct. The pacemaker cells are located in the sinoatrial node.
What other organs produce electrical stimulation?
Our Answer: Some smooth muscle cells in blood vessels can transform stretch into electricity. However, the electrical stimulation in the brain is the best example of a bioelectrical signal.
Learn By Doing #5
What molecule binds to oxygen for efficient transport throughout the body?
- heme
Correct. Oxygen binds to the iron molecule at the center of the planar heme molecule. - water
Incorrect. Oxygen is poorly soluble in water. - lipids
Incorrect. Red blood cells have lipid membranes, but the lipids do not bind to oxygen. - surfactant
Incorrect. Oils are solubilized by surfactants, including bile, but oxygen is not transported by these molecules.
What cells transport oxygen throughout the body?
- immune cells
Incorrect. Immune cells are found near oxygen exchange and in blood vessels to ensure that there are no pathogens exchanged from the environment. - endothelial cells
Incorrect. Endothelial cells are found in the capillaries of the cardiovascular system, but oxygen is carried by red blood cells. - lung epithelium
Incorrect. Oxygen passes through the epithelium of the lung, but is transported through the body by the red blood cells. - red blood cells
Correct. Trillions of red blood cells travel through the body at a time to distribute oxygen.
Where does exchange from the atmosphere to the body occur?
- nose
Incorrect. The nose is where air (and oxygen) enters the respiratory system, but exchange does not occur until the alveoli. - heart
Incorrect. The heart pumps blood which obtains the oxygen from the respiratory system at the alveoli. - alveoli
Correct. The alveoli are higher surface area structures at the terminal branch of the bronchi where oxygen exchange occurs. - trachea
Incorrect. The trachea, or windpipe, is part of the respiratory system, but the thick cellular structures do not allow exchange of oxygen.
Learn By Doing #6
Match the length (or size) scale and the change occurring at that level to the descriptions in the table below.
Length Scales: tissue/organ/body level, environment, cell level, chemical level, population, molecular level
Changes: oxygen, low oxygen levels, occlusion (blockage), β-globin, red blood cells, genetic mutations found in certain groups
| Length Scale (from smallest to largest) | Change | Effect of Change at that Level |
| chemical level | oxygen | The ability to bind this substance is reduced. |
| molecular level | β-globin | This mutated protein is altered in how it binds oxygen. |
| cell level | red blood cells | These cells sickle in low oxygen conditions. |
| tissue/organ/body level | occlusion (blockage) |
This leads to reduced oxygen for tissues and organs in the body. |
| environment | low oxygen levels | Some conditions, such as those found at high altitudes, make the disease more severe. |
| population | genetic mutations found in certain groups | This mutation provides resistance to infection with the malaria parasite. |
Learn By Doing #7
Which of the following isnota carbohydrate that could lead to obesity?
- glucose
- cellulose (Cellulose is indigestible by humans and so cannot contribute to weight gain.)
- starch
- fructose
How is muscle mass lost?
- underutilized muscle fibers die
- underutilized muscle fibers shrink
- underutilized muscle fibers lie dormant and are not used
Which isnota strong contributing factor to the correlation of obesity with lower income individuals of inner cities of the United States?
- reduced air quality from vehicle emissions
- reduced access to nutritious foods versus high calorie, high fat foods
- reduced formal education on healthy habits
Learn By Doing #8
Which of the following changes would result in acidosis?
- increase in blood carbon dioxide concentration
Correct. This would shift the bicarbonate buffer equilibrium towards the right, which would result in greater blood hydrogen concentrations, and subsequently lower pH. - Hyperventilation
Incorrect. This would result in release of greater than usual amounts of carbon dioxide, which would shift the bicarbonate buffer equilibrium to the left. This would result in lower blood hydrogen concentrations, and subsequently greater pH. - Decrease in cellular metabolism
Incorrect. This would result in less carbon dioxide production, which would shift the bicarbonate buffer equilibrium to the left. This would result in lower blood hydrogen concentrations, and subsequently greater pH. - Decrease in blood carbon dioxide concentration
Incorrect. This would shift the bicarbonate buffer equilibrium towards the left, which would result in lower blood hydrogen concentrations, and subsequently greater pH.
Which of the following factors would result in a blood pH disturbance?
- high fat diet
Incorrect. Although increased fat catabolism results in increased fatty acid release (acidosis), there are other factors that would result in a pH disturbance. - severe diarrhea
Incorrect. Although loss of bicarbonate from diarrhea would result in acidosis, there are other factors that would result in a pH disturbance. - heavy exercise
Incorrect. Although heavy activity results in increased amounts of lactic acid and subsequently acidosis, there are other factors that would result in a pH disturbance. - all of the above
Correct. All of the above factors would result in a pH disturbance. A high fat diet results in acidosis via increased fatty acid release; severe diarrhea results in loss of bicarbonate, which causes acidosis; and heavy exercise results in acidosis from lactic acid buildup.
Learn By Doing #9
When you eat a meal high in glucose, there is an increased absorption of glucose from the lumen of the gastrointestinal tract. This results in an increase in blood glucose. Why is such a disturbance in homeostasis transient?
- Glucose levels decrease following increased secretion of GH
Incorrect. Increased release of growth hormone would not affect glucose concentrations. - glucose levels decrease following increased secretion of insulin
Correct. Insulin release causes an increase in cellular glucose uptake. - glucose levels decrease following increased secretion of glucagon
Incorrect. This would have the opposite effect, and result in an increase in blood glucose levels.
Learn By Doing #10
What other compensatory effects would occur within the body during intensive exercise?
- increased breathing rate
Incorrect. Although breathing rate would increase to allow for increased oxygen in the body, there is another correct answer choice here. - increased heart rate
Incorrect. Although heart rate would increase to improve oxygen delivery to muscle tissues and other vital organs, there is another correct answer choice here. - decreased heart rate
Incorrect. Heart rate would increase to improve oxygen delivery to muscle tissues and other vital organs. - both 1 and 2
Correct. Increased breathing rate would increase the amount of oxygen in the body, while increased heart rate would improve delivery of this oxygen to the muscle tissues and other vital organs.
Learn By Doing #11
How would the body deal with reduced red blood cell lifespan to prevent anemia and maintain homeostasis?
- better usage of each red blood cell
Incorrect. There is a limit as to how much one red cell can do; that is why there are trillions in a healthy person at any time. - using other means of oxygen transport
Incorrect. Oxygen is so poorly soluble in water that it needs to be carried in a special way, such as bound to an iron in hemoglobin. - increased red blood cell production by increased hematopoiesis
Correct. The body is stimulated to produce more red blood cells. - more iron per red blood cell
Incorrect. There is a limit as to how much hemoglobin, and therefore iron, can go into each cell.
What type of loop is this ‘downward spiral effect’?
- Negative feed-back loop
Incorrect. Because the release of toxic materials from within the cells triggers further necrosis in surrounding cells, this is a positive feedback loop. Negative feedbacks push the body toward balance. - Positive feed-back loop
Correct. Positive feedbacks, despite the name “positive”, push the body away from balance. In this case, the release of toxic materials from within the cells triggers further necrosis in surrounding cells.
Match the components of the feedback loop described above with their role in the feedback loop.
Components: further release of toxic materials, release of toxic materials, cell injury
- Cell injuryis the initiation event for the feedback loop.
- The stimulus isrelease of toxic materials.
- The effectors that make adjustments in this system arefurther release of toxic materials.
Learn By Doing #12
What do sores on the feet suggest about patient health?
- Overgrowth of the epidermis
Incorrect. There are issues with epidermal growth, especially with the integumentary system, but these are less evident early on. - poor circulation and reduced immune system
Correct. Diabetes can lead to sores that don’t heal. - muscular and skeletal dysfunction
Incorrect. After prolonged diabetes, muscle and skeletal tissues can be altered. however, they are not the first to deteriorate. - Excessive exercise caused by increased blood sugar
Incorrect. Occasionally physical activity can be altered with diabetes, but many times diabetes cause lethargy and fatigue.
Learn By Doing #14
Thinking about lung function, why would excess fat produce shallow breathing?
- excess fat pushes down on the diaphragm, not allowing it to expand
Correct. Excess fat does not allow the diaphragm to fully expand. - excess fat cells in the body require more oxygen. This increased demand makes breathing seem shallow.
Incorrect. While demand may be increased, the shallow breathing is a real symptom. - less fluid production leads to less blood available for oxygen transport
Incorrect. On the contrary, individuals with obesity tend to have greater amounts of blood than individuals of normal body mass. - alveoli become smaller, so less oxygen is transported throughout the body
Incorrect. Decreased size of alveoli is not a symptom of obesity.
Obesity hypoventilation syndrome is a condition caused by failure to breathe rapidly and/or deeply. How could this adversely affect the body?
- low blood carbon dioxide level
Incorrect. Failure to breathe rapidly/deeply would result in high blood carbon dioxide levels. - slow heart rate
Incorrect. Failure to breathe rapidly/deeply would require an increased heart rate in order to compensate for the decreased oxygen intake. - low blood oxygen levels
Correct. Since obese individuals breathe less frequently than healthy ones, they have lower than normal blood oxygen levels. - low blood glucose levels
Incorrect. Failure to breathe rapidly/deeply would not affect blood glucose levels.
Sleep apnea can disrupt regular sleep patterns. Given what you know about sleep patterns, what do you predict will be affected?
- mood
Incorrect. Although sleep apnea can make individuals feel irritable, there are other correct answer choices. - alertness
Incorrect. Although sleep apnea can result in difficulty concentrating and fatigue, there are other correct answer choices. - headaches
Incorrect. Although individuals suffering from sleep apnea tend to have more headaches, there are other correct answer choices. - both 1 and 2
Incorrect. Although sleep apnea can affect both mood and alertness, that is not all it can affect here. - all of the above
Correct. All of the above can be affected by sleep apnea.
Chronic acid reflux can result in mucosal damage, which can lead to gastroesophageal reflux disease (GERD). The risk of GERD is substantially greater in obese individuals. Which of these obesity-related factors would cause this condition or cause it to worsen?
- Eating fatty foods
Correct. Fatty foods take longer to digest, so acid production will occur longer in the stomach. This increases the likelihood of reflux, especially if eaten close to bedtime. - The smooth muscle forming the upper esophageal sphincter degrades
Incorrect. The upper esophageal sphincter is located at the upper end of the esophagus. - Putting excess pressure on the lower esophageal sphincter
Incorrect. Obesity increases inter-abdominal pressure, which increases the frequency of acid reflux. - Esophageal lining becomes more sensitive
Incorrect. This would not affect the tendency of stomach acid to travel into the esophagus.
If an obese individual also smokes cigarettes, how could smoking potentially worsen heartburn?
- Stomach acidity is increased
Incorrect. While nicotine from cigarettes increases stomach acid production, there are additional ways smoking can worsen heartburn. - Saliva production is decreased
Incorrect. While saliva contains bicarbonate, which helps neutralizes stomach acid, there are additional ways smoking can worsen heartburn. - Lower esophageal sphincter function is impaired
Incorrect. While nicotine in tobacco lowers pressure in the lower esophageal sphincter, there are additional ways smoking can worsen heartburn. - All of the above
Correct. All of these are side-effects resulting from smoking that could worsen heartburn.
How does fat from the diet enter the bloodstream?
- Packaged into lipoproteins
Correct. Lipoproteins have hydrophilic groups directed outward, and are able to transport lipophilic fats throughout the body in the blood. - Carried by Islet cells
Incorrect. Islet cells are located in the pancreas and produce glucagon, insulin, somatostatin, amongst other things. - Enter the bloodstream directly
Incorrect. Fats are hydrophobic, and thus are not soluble in blood or water. - Carried by red blood cells
Incorrect. Red blood cells only carry oxygen throughout.
Obesity results in a decrease in high density lipoproteins (HDL). How could this adversely affect an individual’s health?
- Increased risk of heart disease
Incorrect. Decreased HDL levels have been proven to result in an increased risk of heart disease. But this is not the only adverse effect listed here. - Increased risk of stroke
Incorrect. Decreased HDL levels have been proven to result in an increased risk of stroke. But this is not the only adverse effect listed here. - Increased risk of diabetes
Incorrect. While obesity is correlated with an increased risk of diabetes, this is not a direct result of decreased HDL levels. - Increased risk of cancer
- Incorrect. While obesity is correlated with an increased risk of cancer, this is not a direct result of decreased HDL levels.
- Both 1 and 2
Correct. Decreased HDL levels have been proven to result in both an increased risk of stroke and heart disease. - All of the above
Incorrect. Decreased HDL levels have not been proven to result in all of these affects.
Obesity is linked with greater resistance to insulin. How could this potentially result in a greater risk of breast cancer?
- Insulin can trigger the growth of breast cancer cells.
Correct. Insulin resistance results in greater amounts of insulin in the bloodstream, which has been shown to trigger breast cancer. - Glucose in the bloodstream can trigger growth of breast cancer cells.
Incorrect. It is high levels of insulin, not glucose, that are correlated with an increased rate of breast cancer. - Medications used to treat insulin resistance can trigger growth of breast cancer cells.
Incorrect. High levels of insulin in the bloodstream are correlated with an increased rate of breast cancer. - All of the above
Incorrect. Only high levels of insulin in the bloodstream are correlated with an increased rate of breast cancer.
How does retained moisture result in skin rashes and other infections?
- decrease in passive immunity
Incorrect. Passive immunity entails receiving preformed antibodies (i.e. from breastmilk), which does not occur naturally from bacterial infection. - decreased antibody production
Incorrect. Water promotes bacterial growth, which results in an increased immune response. - encourages microbial (bacteria and fungus) growth
Correct. Bacteria and fungi require water to grow, so retained moisture provides optimal conditions for their survival. This can result in a variety of infections. - moisture kills neutrophils
Incorrect. Moisture is not harmful to neutrophils.
When excess fat creates folds in the skin, what will happen to skin within the folds?
- large amounts of perspiration in this area
Incorrect. Sweat glands are obstructed because of the excess folds, resulting in a decreased amount of perspiration in this area. - formation of a tumor within the skin fold
Incorrect. It is highly unlikely that a tumor would form as a result of skin folds. - vitamin D deficiencies from lack of direct sunlight
Incorrect. Although obesity has been linked to lower levels of vitamin D, this symptom is not caused by skin folds. - formation of a heat rash
Correct. When sweat glands are obstructed, perspiration can get trapped within the layers of the skin. This results in germ build-up, which can cause a rash.
What causes the symptoms of dehydration and thirst in individuals with higher blood glucose levels?
- Free glucose inhibits cells from absorbing water.
Incorrect. The presence of free glucose does not affect a cell’s ability to absorb water. - Cells require more water to produce glucagon.
Incorrect. Glucagon is a hormone that raises blood glucose levels. Individuals with high blood glucose would release insulin, not glucagon. - Glucose increases osmotic pressure of the urine.
Correct. Increased osmotic pressure in the urine reduces the kidney’s ability to reabsorb water. This leads to dehydration and increased thirst. - All of the above
Incorrect. Only one of the above answer choices is responsible for the symptoms of dehydration and thirst in individuals with higher blood glucose levels.
Osteoarthritis can occur in individuals who engage in high risk sports as well as those who are sedentary but obese. Why is this?
- increased synovial fluid from increased adrenaline production
- increased synovial fluid production from increased load and use
- both 1 and 2Correct. Both situations can add strain and extra load on joints, which will lead to increased synovial fluid around the joint.
Which of the following are not causes of poor circulation?
- Increased release of histamine
Correct. This would result in vasodilation and would result in unobstructed blood flow. - Thrombus formation
Incorrect. When blood clots form inside a blood vessel, the flow of blood through the body is obstructed. - High cholesterol levels in blood vessels
Incorrect. High cholesterol levels could result in blood vessel constriction, resulting in obstruction of blood flow. - Arteriosclerosis
Incorrect. Hardening of the arteries makes it difficult for the blood to move from the heart to the extremities, such as the hands and feet.
Did I Get This #1
Which of these factors is directly responsible for the high incidence of breast cancer in older, obese women?
- Breast tissue becomes more sensitive to estrogen
- Buildup of fat tissue around the breast results in tumor formation
- Reduced number of hormonal receptors on breast tissue cells
- Large amounts of fat tissue produce lots of estrogen(After menopause, the ovaries stop producing hormones, which puts the burden of estrogen production on fat tissue. Since obese women have greater amounts of fat tissue, their estrogen levels are higher.)
How else can excess fat affect negatively affect the body?
- Back and spinal pain
- Pain in muscles of the upper chest and throat
- Arthritis in the joints
- All of the above
Which of the following conditions is not a potential result of obesity?
- acanthosis nigricans
- cellulitis
- callus
- contact dermatitis
What is the link between obesity and insulin insensitivity in cells?
Our Answer: Diets consisting largely of intake of large amounts of fats and simple sugars can result in insulin resistance. Body cells are desensitized to the normal actions of insulin, and are thereby unable to uptake glucose, amino acids and fatty acids, which begin to leak out of the cells. In order to account for this insulin insensitivity, larger concentrations of insulin circulate in the bloodstream. When insulin spills over into the skin, abnormal growth increases occur, referred to as hyperplasia of the skin. This condition is typically associated with type 2 diabetes, obesity, and polycystic ovary syndrome, to name a few examples.
Media Attributions
- obesity-hotspot2
