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What is a thrombus and how is it different from an embolus?
Thrombus is a fixed blood clot and is different from an embolus bc it does not freely travel through the vasculature
Describe the three layers of the wall of a blood vessel. How do they differ between arteries, veins, and capillaries? Which vessels have valves and why?
1. Tunica intima – endothelial lining
2. Tunica media – smooth muscle & elastic fibers
3. Tunica adventitia – connective tissue around the outside
Capillaries are almost all endothelial lining
Arteries mostly smooth muscle and elastic tissues
Veins have valves to prevent backflow since pressure is so low
What is a portal system? What is the usefulness of these systems?
· Portal system is when 2 capillary beds are linked together without going to heart
· Hepatic Portal system – links stomach and intestines to liver so that things can be detoxed and gylcogen stored before going to heart
What is a precapillary sphincter and what does it do?
· Control flow to capillaries. If constricted, flow bypasses capillaries and continue through arterioles (away from heart)
What is a metarteriole and what does it do?
· Metarteriole brings blood to capillaries and runs right next to the capillary bed (blood flow away from the heart)
What is the difference between fenestrated and unfenestrated capillaries?
· Fenestrated: more leaky capillaries (sinuses, liver, spleen)
· Unfenestrated: less leaky capillaries (blood/brain barrier, blood/testes)
What is angiogenesis? What stimulates it?
· Angiogenesis is the creation of new blood vessels in the body.
· Controlled by cytokines and stimulated by growth factors such as vascular endothelium growth factor and fibroblast growth factor
What factors affect blood flow?
· Resistance via viscosity (hematocrit), vessel length, vessel diameter
What is the difference between laminar blood flow and turbulent blood flow?
· Laminar blood flow is smooth and doesn’t have swirls
· Turbulent blood flow is “noisy” as a result of some obstruction to flow causing swirls in flow. Not as efficient at delivering blood.
What might cause the turbulent blood flow? How would a clinician be able to detect turbulent blood flow?
· Can be caused by build up of plaque or cots. Clinicians can detect these by listening for bruits through a stethoscope.
What is peripheral vascular resistance? What factors affect PVR? Which have the greatest influence on PVR?
· Peripheral vascular resistance is the measure of friction blood encounters as it passes through vessels
· PVR is affected by blood viscosity, vessel diameter, and vessel length
· Vessel diameter has the greatest effect
How do changes in PVR affect BP?
· Increase in PVR means an increase in blood pressure usually.
What is Poiseuille’s Law?
· R = 8Ln/pr4
Define systolic and diastolic BP. What are normal values for this?
· Systolic bp= blood pressure when heart is in contraction (120)
· Diastolic bp= blood pressure when heart is at rest (80)
What is pulse pressure? What is mean arterial pressure & what factors affect it? Be able to calculate both of these without a calculator.
· Pulse Pressure = systolic P – diastolic P
· MAP = diastolic P + 1/3(systolic P – diastolic P)
What factors affect arterial BP?
o Fluid intake, Fluid loss
Effectiveness of the heart as a pump (cardiac output)
o Heart rate
o Stroke volume
Resistance in the arterioles
o Arteriole diameter
Distribution of blood between the veins and arteries
What is afterload and what produces it? How does it affect CO?
· Afterload is how hard the heart as to work to get the blood out to the body from the heart. This has to do with how hard the blood in the arterial system is pushing back on the ventricles.
What is HTN?
· Consistently elevated BP
· >140/90 on repeated measurements
What are Korotkoff sounds and what are they used for?
· Created by pulsatile blood flow through the arteries
· Used for determining systolic and diastolic blood pressure
How does the body regulate BP?
· Change in cardiac output (decrease in CO=decrease in BP)
· Vasodilation=decrease in BP
· Vasoconstriction=increase in BP
· More excretion of fluid in urine=decrease in blood volume=decrease in bp
What are baroreceptors and where are they found?
· Baroreceptors are pressure receptors and are found in the carotid and aortic arteries
· Send message to medulla
What substances act as metabolic vasodilators (tonic control of arteriole diameter)?
· Nitric oxide
· Hypoxic- Adenosine
How does the sympathetic NS affect BP?
· Norepinephrine: increase in NE decreases areteriole diameter and thus increasing BP and CO
How does the body regulate blood flow to the various organs?
· Precapillary sphincters direct flow away (constriction) or towards (dilation) certain capillary beds
Through which type of blood vessels is blood flow the slowest and why?
· Veins (vena cavae)
· Furthest away from the force generator of the heart (reason for flow) and only thing helping movement is one way valves and smooth muscle
What is bulk flow and what causes it?
· Mass movement in the capillaries as a result of hydrostatic or osmotic pressure gradients
What is the difference between absorption and filtration? Where in capillaries does each of these occur?
· Absorption: fluid movement INTO capillaries (at venous end)
· Filtration: fluid movement OUT of capillaries (at arterial end)
What are lymph vessels and what do they do?
· Lymph vessels flow in one directions
· Returns fluid & proteins to circulatory system
· Picks up fat absorbed & transfers it to circulatory system
· Serves as filter for pathogens
What is edema? What are some of its causes?
Swelling caused by a buildup in fluid in the body’s tissues
o Inadequate drainage of lymph
o Filtration >>> absorption (Increase in hydrostatic pressure)
What is the baroreceptor response to hypertension and hypotension?
o Less NE released (vasodilation, decreased force of contraction via ventricular myocardium)
o More ACh released (decreased HR through SA node, decrease BP)
What is CHF? What happens if there is right-sided failure (i.e., low CO from the right ventricle)? What happens if there is left-sided failure (i.e., low CO from the left ventricle)?
· CHF stands for congestive heart failure, a situation in which the heart cannot pump enough blood. IF there is a right side failure, blood will not get to the lungs and there will be systemic edema. If there is a left side failure, not enough blood will be getting to the body and there will be pulmonary edema.
What is the renin-angiotensin system, and how does it regulate BP?
· Either conserving fluids or eliminating them via kidney
· Regulation of fluid excretion (more fluid excretion=decrease fluid volume=decrease blood volume=decrease in BP)
What is an ACE inhibitor and why is it used to treat hypertension?
ACE inhibitors block the conversion of AI to AII. This: lowers arteriolar resis and increase venous capacity; decrease CO, cardiac index, stroke work, and vol; lower resistance in blood vessels in the kidneys; and lead to increased excretion of sodium in the urine. Renin will inc concentration in the blood as a result of neg feedback of conversion of AI to AII. AI will increase for the same reason. AII and Aldosterone will dec. Bradykinin will increase bc of less inactivation that is done by ACE.
What is aldosterone and what organ produces it? What stimulates its release and what does it do?
· Aldosterone plays a central role in the regulation of blood pressure mainly by acting on the distal tubules and collecting ducts of the nephron, increasing reabsorption of ions and water in the kidney, to cause the conservation of sodium, secretion of potassium, increased water retention, and increased blood pressure.
· Aldosterone is produced by the adrenal gland and is made after the stimulation by angiotension
What is ANP and what organ produces it? What stimulates its release and what does it do?
· Atrial natriuretic peptide promotes sodium and water excretion, and it is produced by the myocardial cells in the artia of the heart.
What is ADH? What brain region produces it and from what organ it is released? What stimulates its release and what does it do?
· ADH is anti diuretic hormone, and it is produced in the hypothalamus and it is released from the posterior pituitary. Decreased BP, decreased blood volume, and high osmolarity can cause its release and it works to increase water reabsorption to conserve water.
What are the functions of the respiratory system?
o Also in the kidneys
Condition inspired air
Protection against inhaled pathogens
What structures are involved in preparing inspired air to enter lower respiratory structures and what do they do?
· The upper airways and bronchi are the main areas where the protection happens, including the nose, trachea, and bronchi. These areas work to warm, humidify, and filter the incoming air.
What is the epiglottis?
· Flap in throat
· In this manner it prevents food from going into the trachea and instead directs it to the esophagus, which is posterior.
What is the difference between ventilation and respiration?
Ventilation: movement of air into & out of body
Respiration: gas exchange
o External respiration: gas exchange between lungs and capillaries
o Internal respiration: gas exchange between tissues and capillaries
Where does internal respiration occur? External respiration?
· Internal respiration occurs in the tissues and capillaries of the body
· External respiration occurs in the alveoli of the lungs between the lungs and capillaries
What is the difference between the conducting zone and respiratory zone? What structures are associated with each?
Conducting zone: no gas exchange occurs (dead zone is up through bronchioles)
Respiratory zone: gas exchange occurs (alveoli)
What muscles are involved in normal inspiration, normal expiration, forced inspiration, and forced expiration? What is the major muscle of breathing and what nerve innervates it?
· Normal inspiration: diaphragm & external intercostals
· Normal expiration: entirely passive
· Forced inspiration: . Forced inhalation uses the same with the inclusion of the scalenes and the sternocleidomastoid
· Forced expiration: internal intercostals as well as the abdominal muscles.
· Major muscle of breathing: diaphragm
What is the pleural membrane and what is its role in lung inflation?
· Encapsulate fluid that allows for easy sliding movements but also prevents separation from the membrane (example with water on the glass slides)
· Link lung to wall of thoracic cage
What is a pneumothorax and what might cause one?
· Rupture in the membrane, sealed pleural cavity is opened
· Might be caused by trauma, knife wounds, etc
How does the airway structure change as you go from the upper airway deeper into the lower airways?
From upper to lower
o Structures become more numerous
o Structures become less and less in diameter
o Number of divisions in those structures become more and more
What is the difference between a type I pneumocyte and a type II pneumocyte?
· Type I: gas exchange
· Type II: synthesizes surfactant (lower surface tension and allow for easier movement)
How is pressure related to volume (Boyle’s Law)?
· Gas pressure is inversely proportional to volume
· P1V1 = P2V2
What is the partial pressure of a gas (Dalton’s Law)?
· Pgas = Patm ´ % of gas in atmosphere
Know what the following terms indicate and be able to identify them on a spirometry tracing: TV, IRV, ERV, VC, Residual volume.
· TV: Tidal volume (normal inspiration and expiration)
· IRV: inspiratory reserve volume (volume above normal inspiratory range)
· ERV: expiratory reserve volume (volume below normal expiratory range)
· VC: vital capacity (IRV-ERV)
· Residual volume: volume that is always in there
What is minute volume?
· This represents the amount of air that is moved within the lungs in one minute.
What volume and pressure changes occur in the lungs during normal inspiration and expiration?
· Alveoli: Negative pressure during inspiration, positive pressure during expiration
· Volume moved: greatest on cusp of inspiration to expiration, least on cusp transition of expiration to inspiration
Why is the intrapleural pressure always negative with respect to atmospheric?
· Intaplural pressure is always about 3 mmHg low because of the combo of outward pull of the thoracic cage and the inward recoil of the elastic lungs.
What is compliance? What does it mean if the lungs have low compliance?
Compliance is the ability to stretch
o Stretches easily
o Requires more force
o Restrictive lung diseases
o Fibrotic lung diseases and inadequate surfactant production
What is surface tension? How does surfactant affect surface tension in the lungs? What happens to alveoli if there is a deficit in surfactant?
Surface tension is created by the thin fluid layer between alveolar cells and the air.Surfactant is more concentrated in smaller alveoli
o Reduces surface tension – prevents alveolar collapse
o Mixture containing proteins and phospholipids
Deficit in surfactant: If there is a deficit in surfactant, surface tension will increase and more work will be needed to expand the alveoli.
What changes in the upper airway affect resistance and airflow? What changes in the lower airway affect resistance and airflow? Why might these differ?
· Changes in upper airway: mucus in the upper airway
· Changes in lower airway: changes in bronchiole diameter (bronchoconstriction (PNS), histamine, leukotrienes)
How does the ANS affect airway resistance?
· The ANS can both constrict and dilate the bronchioles of the airway. Parasympathetic innervation can cause the constriction of bronchioles, whereas sympathetic control by epinephrine can open up and relax the bronchioles.
How does total alveolar ventilation differ from total pulmonary ventilation (minute volume)?
Total pulmonary ventilation/minute volume:
o Alveolar ventilation = RR ´ (tidal vol – dead space vol)
Why is ventilating the anatomic dead space considered a cost of ventilation?
· This is because ventilating this space is sending air over areas that do not exchange gases with the blood. It takes into account the amount of fresh air that never actually reaches the exchange surface.
Know what the following terms mean: eupnea, hyperventilation, hypoventilation, dyspnea, apnea
· Eupnea: normal breathing
· Hyperventilation: Increase in RR &/or volume w/out an increase in metabolism
· Hypoventilation: decrease in alveolar ventilation
· Dyspnea: difficulty breathing
· Apnea: no breathing
How does hyperventilation affect PO2 and PCO2 in the alveoli? How does hypoventilation affect these?
o Increase in PO2 and decrease in PCO2
o Decrease in PO2 and Increase in PCO2
What is ventilation-perfusion matching?
· Levels of oxygen and carbon dioxide locally control dilation and constriction of arterioles and bronchioles
How does blood flow to the pulmonary arterioles change with changes in PO2 and PCO2? Is this the same or different from changes in the systemic circulation under the same oxygenation/CO2 status?
· If PCO2 goes up, bronchioles dilate and so do systemic arteries. If PO2 goes up, bronchioles constrict and so do systemic arteries. It is basically opposite occurences for pulmonary and systemic arteries, as well as increases to decreases in PO2 or PCO2.
What factors affect the diffusion of a gas into a liquid?
· Surface area
· Concentration gradient
· Membrane thickness
· Diffusion distance
· Pressure gradient
Which gas is more soluble in liquid: CO2 or O2?
· CO2 (why oxygen is carried predominantly by hemoglobin)
Know normal blood gas values (PCO2 and PO2) in the arterial and venous system as well as in the lungs (alveolar) and in the tissues.
· Arterial: PO2 85-100mmHg, PCO2 35-45mmHg
· Venous: PO2 40-100mmHg, PCO2 46mmHg
· Alveolar: PO2 100mmHg, PCO2 40mmHg
· Tissues: PO2 40mmHg, PCO2 46mmHg
What is hypoxia? What are some of the things that can result in hypoxia?
Deficiency in the amt of O2 reaching the tissues
Causes: Emphysema/destruction of alveoli: destruction of alveoli results in decreased SA for gas exchange to occur
o Fibrotic lung disease: thickening of alveolar membrane slows gas exchange
o Pulmonary edema: fluid in interstitial space increases distance of diffusion
o Asthma: constriction of bronchioles restricts amount of oxygen to alveoli
What are some of the ways that alveolar ventilation is altered and what causes them?
· Decreased lung compliance, increased airway resistance, or drug overdoes that cause CNS depression.
How is most of the oxygen carried in the blood? CO2?
Bound to hemoglobin
How does hemoglobin affect oxygen carrying capacity?
· Since majority (over 98%) of oxygen is bound to hemoglobin, body is restricted in its ability to carry so much oxygen by the amount of hemoglobin in the body
How many molecules of oxygen can 1 molecule of hemoglobin carry?
What is the difference between PO2 and oxygen saturation (SaO2)? How does a change in PO2 affect SaO2?
· PO2 is the partial pressure of oxygen
· Oxygen saturation is the attraction of oxygen to the hemoglobin
· As the partial pressure of oxygen decreases, hemoglobin releases oxygen molecules
How does pH affect oxygen dissociation and what is the Bohr effect? How is this biologically relevant?
· At a lower pH, hemoglobin loses oxygen easier
· Allows for the open site to bind to hydrogen ions to decrease the pH and work as a buffer
What other substances affect oxygen binding to hemoglobin and how is this biologically relevant?
· Temperature: at lower temps, harder to dissociate O2 from hemoglobin. At high temps, easier to separate the two
· PCO2: higher PCO2 makes hemoglobin less attracted to oxygen than lower PCO2 levels
· Biologically relevant since hemoglobin can also be a CO2 carrier and thus a buffer (dissolved CO2 via bicarb creates acidic environment)
How does fetal hemoglobin differ from adult and why is this important? How does this lead to changes in bilirubin level in the postnatal phase? Why might it lead to jaundice?
Fetal hemoglobin has a higher affinity for oxygen than an adult usually does, since oxygen levels in the placenta can be low. It begins to immediately be replaced by normal hemoglobin in the postnatal phase, meaning there must be destruction and replacement of a lot of red blood cells in a short amount of time. The increase in bilirubin that we would expect to see in this case can cause the skin and whites of the eyes to become yellowed, a condition known as jaundice
Know how increased CO2 affects pH and bicarb levels.
Increase in CO2 brings and increase in hydrogen ions and bicarb thus bringing an increase in pH (carbonic anhydrase is fastest enzyme in body)
What is the chloride shift and where does this occur?
· Occurs in the RBC membrane
· Cell trades one chloride ion for one bicarb ion to either move it in or out of the cell (helps carbonic amylase do its job with converting CO2 and water to bicarb, or even the reverse reaction
How are changes in blood gases detected and how do they affect ventilation?
Detected by chemoreceptors
Respiratory control center in pons and medulla
o Pons takes sensory info and acts on respiratory control center to modify activity, Don’t exactly know how the reflexes all work
o dorsal respiratory group (found in nucleus tractus solitarius (NTS), Activates prenic nerve (diaphragm) and also external intercostals, Or ventral respiratory group, Involved in keeping airways open, Forced breathing as well
Which has a greater affect on ventilation: change in O2 or change in CO2 levels?
Change in CO2
What CNS structures affect ventilation? Which affects inspiration and which affects expiration?
· Medulla and pons
· Inspiration: medulla
· Expiration: medulla
· Pons modulates the process
How does an increase in PCO2 affect ventilation and why?
· Acts via central chemoreceptors in the brain
· Found in medulla
· Respond to changes in cerebral spinal fluid
· Increase in PCO2 causes increase in CO2 levels (bc of diffusion across capillary wall) and indirectly detected by changes in hydrogen ion levels
Bicarbonate is often given in code situations where the patient has had a prolonged period of cardiac and respiratory arrest. Why might this be the case?
· Because increasing the pH of the body can cause the hemoglobin to have higher affinity for oxygen. This can get necessary blood to organs that have been deprived for a long time.
What cells secrete leptin and what does it do? Neuropeptide Y? Ghrelin?
· Leptin is secreted by adipose cells and it acts as a negative feedback system to tell the brain to decrease food intake. Neuropeptide Y is what appears to be the stimulus for food intake in the brain. Leptin normally inhibits NPY in a negative feedback pathway. Ghrelin is a peptide secreted by the stomach during fasting which increases hunger. CCK and GLP 1 decrease hunger.
When it was first discovered, it was hoped that leptin might become a treatment for obesity. Why didn’t this work? How would you expect leptin levels to be altered in an obese individual and why?
· It didn’t work because only a small percentage of people who are obese are leptin deficient. You would expect their levels to be very high because they have high levels of fat stores, which would cause adipose cells to release more leptin.
What are the 4 layers of the wall of the GI tract and what major structures do they contain?
o Epithelium, Connective tissue
o Longitudinal muscle, Circular muscle
o Lamina propria
o Muscularis mucosae
What is the enteric NS and what are its 2 components?
· Called the “Little Brain,” responds to local stimuli and messages from the brain
o Sensory receptors and neurons
o Neurons of myenteric and submucosal plexuses
What are slow wave potentials and how do they affect the force of contraction created by the GI tract?
· They are the cycles of smooth muscle contraction in the GI tract that are made of spontaneous depolarizations and repolarizations; very slow, especially compared to pacemaker potential of myocardial cells. The longer the duration of the slow wave potential, the longer the duration of contraction. The longer the duration of the potentials will also create a stronger contraction.
What is the migrating motor complex (MMC) and what is its function?
· The migrating motor complex is a housekeeping function that sweeps food remnants and bacteria out of the upper GI tract and into the large intestine. It is a series of contractions after a meal that begins in the stomach and goes all the way to the large intestine.
What are peristalsis and segmentation?
· Peristalsis: Wave-like contraction of muscle to encourage movement
· Segmentation: alternating contractions that cause no net movement but encourage mixing
What are the components of saliva and what does it do?
. Breaks down starches
· Cleanses the mouth
· Moistens & dissolves food chemicals
· Aids in bolus formation
o salivary amylase
o lingual lipase
o lysozyme, defensins, IgA
What organ contains rugae and what is their purpose?
· Rugae are in the stomach and are foldings
· Increase surface area and allow for extra stretch of the stomach
What do the parietal and chief cells of the gastric glands secrete and what is their function?
· Parietal cells: Secrete gastric acid to keep low pH in stomach (via hydrogen pump on membrane of cell)
o Breaks down contents of stomach
· Chief cells: secrete pepsinogen which turns into pepsin when in contact with acid to break down proteins
What do the mucous neck cells in gastric glands secrete and what is the purpose of this secretion?
· Mucus layer to cover lining of stomach so that damage doesn’t occur (like ulcers)
· They secrete mucus and bicarbonate, both of which act to form both physical and chemical barrier to protect the gastric mucosa from the low pH.
What is the long reflex, what major nerve is involved in this, and how does it regulate gastric activity?
· The long reflex is the reflex that comes from the medulla oblongata when the body senses food via sight, smell or taste. It travels down the preganglionic parasympathetic neuron in the vagus nerve into the enteric plexus. Then it goes from here out postganglionic PS and intrinsic enteric neurons to the effector cells, which promote secretion and motility.
What is the short reflex and how does it regulate gastric activity?
· Stimulated within stomach itself, like acid triggering release of pepsinogen by chief cells to break down proteins
· Short reflexes work by distension or sensing peptides and amino acids in the lumen of the stomach. This sensory input then goes to the enteric plexus, and travels to effector cells the same way long reflexes do.
What types of stimuli activate the long reflex?
· Sight, smell, taste, thought of food initiate Cephalic reflexes in medulla
What is the postprandial alkaline tide and what causes it?
· The bicarbonate in the parietal cells leaves through the capillaries
o Causes capillaries around stomach to be more basic than elsewhere
What prevents the acidic gastric secretions from eroding the gastric epithelium?
Thick mucus layer
What structural modifications increase surface area and what is the function of this?
· Villi in the small intestine, rugae in the stomach
· In the stomach, greater surface area allows for greater stretch potential
· In the small intestine, greater surface area allows for an increase in nutrient absorption from the contents
What is the difference between villi and microvilli?
· Villi: major foldings of the lining of the small intestine
· Microvilli: the foldings on the surface of each individual cell lining the villi
What are Peyer’s patches, where are they found, and what do they do?
· They are groups of lymphoid tissue in the intestine. They play an important role in immune response in the last part of the intestine, the ileum.
What is the function of the central lacteal in intestinal villi?
· Transport fats to the lymph
Why is the pancreas considered a mixed gland?
Because it secretes both enzymes and hormones
What are the secretions of the exocrine pancreas and what do they do?
· Bicarbonate: help neutralize stomach acid in first part of small intestine
· Trypsinogen: break down proteins
· Pancreatic lipase: break down fats
· Pancreatic amylase
What are the secretions of the endocrine pancreas and what do they do?
· Insulin: facilitate transport of glucose into cells for use and storage (adipocytes, liver cells)
· Pancreatic polypeptide
Where does most nutrient absorption occur in the GI tract?
What major blood vessels supply the liver with blood, how do they differ, and what is their function?
· Hepatic artery: supplies liver cells with oxygenated blood
· Hepatic portal vein: vein from gi tract goes to liver first for detox
o absorbed nutrients from gut & hgb breakdown products from spleen
What is the gallbladder and what does it do?
· Gallbladder stores bile to be used in intestines
What is the function of the large intestine?
· Absorption of water and breakdown products from bacteria
What are the functions of the following GI hormones: CCK, secretin, gastrin, motilin, GIP, GLP-1, and histamine.
||| CCK: respond to fats and proteins, stim pancreatic enzyme secretion, stimulates gall contraction; inhib gastric emptying and acid secretion.
||| Secretin: responds to acid, stimulates pancreatic bicarb secretion ||| Gastrin: assist digestions and absorption of nutrients ||| Motilin: stimulates MMC
||| GIP: responds to carbs, stops acid secretion and initiates insulin secretion from pancreas
||| GLP-1: responds to carbs, initiates insulin secretion
Histamine: stimulates gastric acid secretion |||
What is amylase, where is it secreted, and what does it do?
· Amylase is an enzyme found intestines that breaks down long glucose polymers into smaller glucose chains and maltose disaccharides.
· Found in saliva, secreted by salivary glands
How does glucose enter the bloodstream, and how is this regulated?
· Uses SGLT=sodium glucose transporter (allows glucose to get into cell, on surface)
· Glucose enters the bloodstream through intestinal mucosa using GLUT transporter (not reliant on insulin) and then into the capillaries
· Regulated via GLUT transporter
How are peptides and amino acids absorbed?
· They must first be broken down. Di and tri peptides can then be cotransported with hydrogen ions. Amino acids cotransport with sodium and small peptides cross via transcytosis.
How are fats absorbed and what is the role of bile salts in this?
· Fats absorbed afters breakdown via lipase, fatty acids then absorbed into cells via diffusion
· Combine with Cholesterol and protein to create chylomicron
o This can then be packaged and sent throughout the body
o Can’t be transported into the capillaries
o Get picked up by lacteals instead and transported via lymph system
Which endocrine organs are considered mixed glands and why?
· Organs that secrete both endocrine and exocrine secretions are known as mixed glands. The glands that fall into this category are the pancreas,
How are hormones classified chemically?
· Peptide/protein hormones
· Steroid hormones
· Amino acid derived hormones
What is a preprohormone? A prohormone? Where are each of these found in the cell and how do they differ from a mature hormone?
· Preprohormone: contains one or more copies of a peptide hormone (needs to be cleaved into final purpose), found outside ribosome
· Prohormone: the inactive molecule that is the prehormone minus the signal sequence, packaged in the golgi
What is the difference between constitutive and regulated release?
· Constitutive release: released continuously
· Regulated release: release initiated by some signal/stimulus
What types of signal transduction do peptide hormones use? How does this differ from steroid hormones?
Peptide hormones use second messengersSome steroid hormones enter the cell and activate itself, others that cannot diffuse use second messengers
What is a binding protein? What types of hormones use these and why are they important?
· Bind to transport molecules or signaling molecules like hormones
· Usually bind to peptide hormones bc cant go through membrane (some steroid hormones that are bound to other things)
What hormones are derived from tryptophan? Tyrosine?
· From tryptophan: melatonin (fuck yeah, cuddling), serotonin
· From tyrosine: Catecholamines (epi, nor epi, dopamine) and Thyroid hormones (T3 and T4)
Trace an endocrine reflex pathway.
· Stimulus signal – acts on gland – secretes hormone – hormone travels to site - hormone acts on site – causes some sort of change at site – decrease in stimulus creates negative feedback
What is an endogenous hormone? Exogenous? Why can administration of an exogenous hormone cause atrophy of an endocrine organ?
· Endogenous: Hormone whose source is from within the body’s cells
· Exogenus: substance coming from outside the body
o Organ could atrophy with addition because negative feedback is turned on artificially, if continues for some time the cells that naturally produce the hormone decrease in size (atrophy)
What is down regulation and how does it affect the response to a particular hormone?
· Down regulation is when the presence of some substance inhibits the response
· Decrease in stimulus usually down regulates the hormone release
How does the hypothalamus influence the pituitary?
· Acts directly on it via the portal system between the hypothalamus and the pituitary
What is the difference between a long-loop and short-loop feedback mechanism?
· Long-loop: occurs when the last hormone of the pathway feeds back to suppress secretion of its trophic hormones.Short-loop: occurs when pituitary hormones feedback on the hypothalamus to decrease its secretion of hormones, effectively stopping the pathway before it makes a full loop
How is the posterior pituitary influenced by the hypothalamus? What are the paraventricular and supraoptic nuclei?
· Neural signals received directly from Paraventricular (PVN) & Supraoptic nuclei (SON); axons end in posterior pituitary and begin in hypothalamus
What hormones are released from the posterior pituitary? Where are they made and what do they do?
· Both made by PVN and SON
· Oxytocin: Causes smooth muscle of the reproductive tract to contract
· Anti-Diuretic Hormone (ADH, vasopressin): Causes water reabsorption in kidney
What is the hypothalamic-hypophyseal portal system?
· Blood passes from the hypothalamus to the pituitary before going anywhere else in the body
How does the hypothalamus regulate secretion of hormones from the anterior pituitary?
o Stimulated by GHRH & inhibited by GHIH (somatostatin)
What hormones are made in the AP and what does each of them do?
· Growth Hormone (GH) – acts on bones & muscles; increases blood glucose
What is acromegaly? Gigantism? What are their causes?
· Acromegaly: Excess GH after epiphyseal closure, leads to facial growth and abnormalities
· Gigantism: Excess GH prior to epiphyseal closure, very big person
What is different about the secretion of prolactin than most other anterior pituitary hormones?
· Constantly being released (constitutively released) and is under tonic negative control, unlike most hormones
What is a thyroid follicle? Colloid?
· Thyroid follicle: Large structures called follicles produce thyroid hormone
· Colloid: on the interior of the follicle cells, where molecular components of follicles are put together
How is thyroid hormone made? What is the difference between T3 and T4? Which one is more potent?
1. Follicular cell synthesizes enzymes and thyroglobulin for colloid, 2. is co-transported into the cell with Na+ and transported into colloid.
3. Enzymes add iodine to thyroglobulin to make T3 and T4.
4. Thyroglobulin is taken back into the cell
5. Intracellular enzymes separate T3 and T4 from the protein.
6. Enter circulation
What regulates the synthesis and secretion of TH?
1. TRH from hypothalamus
2. TSH from anterior pituitary
3. TH from thyroid gland
What does TH do?
· Thyroid hormone in adults has the main function of producing substrates for oxidative metabolism, meaning they are essential for the normal growth and development, especially of the nervous system. In children, it is essential in the full expression of growth hormone.
What would happen if there were too much or too little TH being produced?
· Too much: Negative feedback to hypothalamus (TRH) and anterior pituitary (TSH)
· Too little: No negative feedback, so release of more TRH and TSH
What is a goiter? What might cause a goiter to develop?
· A goiter is a severe enlargement of the thyroid glands
· Might be caused by a decrease in iodine in the diet bc then can’t produce T3 and T4, causing TSH to increase and gland to enlarge
What is calcitonin, what gland produces it, and what does it do?
· Produced by parafollicular cells
· Stimulus is high plasma calcium
· Promotes deposition of calcium into bone
What is parathyroid hormone, what gland produces it, and what does it do?
· Essential for life
· Regulate homeostasis by responding to low levels of calcium
· Need it for NTs release and many other functions like birth
· Acts on kidney
· Acts on gut through calcitrol
What is calcitriol, what does it do, and what is its relationship with PTH?
· Calcitrol – vitamin D3
· Enhances calcium uptake from small intestine
· Enhances renal reabsorption of calcium
· Helps mobilize calcium from bone
· Regulated by PTH
What are the regions of the adrenal gland? What are the main hormones produced in each region? What does each of these hormones do?
· Cortex – steroid secretion
o Adrenal Cortex has 3 layers:
o 1. Zona glomerulosa - Aldosterone
o 2. Zona fasciculata - Cortisol
o 3. Zona reticularis - Androgens
· Medulla - catecholamines
How is cortisol used therapeutically?
· As an anti-inflammatory
What happens if there is too much cortisol present and what are some of the causes of this condition?
• Redistribution of fat
• Thin skin with abdominal striae
• Capillary fragility
• Muscle wasting & weakness
• Insulin resistance
• Suppression of immune system
What happens if there is not enough cortisol present?
· Unable to conserve sodium when we need to
· Tend to look tan because of increase ACTH that also can stimulate melanocytes
What are the two main hormones involved in glucose homeostasis? Where are they produced and what do they do?
· Glucagon: Initiate break down of glycogen stores and glucose into bloodstream
· Insulin: facilitate blood glucose into adipocytes and liver cells for storage as glycogen
· Both produced in pancreas
What hormones are involved in water homeostasis? Where are they produced and what do they do?
· The only hormone involved in water homeostasis is ADH or vasopressin. It targets the kidney to reduce the amount of water excreted. It is produced in the hypothalamus and released via the posterior pituitary. ANP also produces higher excretion levels of water.
What hormones are involved in sodium homeostasis? Where are they produced and what do they do?
· Aldosterone and atrial natriuretic peptide (ANP). ANP is produced in special myocardial cells and causes the excretion of sodium. Aldosterone is synthesized in the adrenal cortex and promotes the reabsorption of sodium from the kidneys.
What are Sertoli cells? Where are they found and what do they do?
· AKA: nurse cells, sustentacular cells
· Found in the testes
· Envelop developing sperm cells (purple)
o Androgen binding protein (ABP) Inhibin
· Form blood-testes barrier
What are Leydig cells? Where are they found and what do they do?
· AKA: interstitial cells
· Secrete testosterone
· Stimulated by LH (leutinizing hormone) from anterior pituitary
What is the mechanism of erection?
· ACh & NO initiate/ maintain erection
· Sympathetic NS causes arterial smooth muscle to contract, cavernosa drains
· PNS - smooth muscle relaxes & arteries fill
· Cavernous tissue presses against tunica albuginea & veins are compressed
What are the central (helical) arteries and the tunica albuginea and what are their roles in erection?
· The central arteries are the arteries that flow through the corpora cavernosa and fill the spongy tissue with blood. The tunica albuginea is the connective tissue that surrounds the corpora cavernosa and allows the penis to erect into its proper elongated shape.
What type of muscle is found in the male reproductive tract?
· Thick smooth muscle
Trace the path of sperm from the seminiferous tubules out of the body.
· Testis to vas deferens to (products from seminal vesicles) to urethra
What are the seminal vesicles, prostate gland, and bulbourethral glands? What types of secretions does each produce?
· Seminal vesicles: Secretions: Fructose & nutrients, Prostaglandins, Enzymes
· Prostate: Receives sperm from seminal vesicles, further dilutes sperm, Secretions: Diluent for sperm transport, Acid phosphatases, citric acid, fibrinolysin, amylase (Secretions Testosterone-dependent)
· Bulbourethral glands: AKA: Cowper's glands, produce and secrete mucus secretions that precede semen
Why does enlargement of the prostate lead to urinary difficulties?
· Because the prostate surrounds the urethra, when it enlarges it compresses that vessel and makes it difficult for urine to get from the urinary bladder to where it exits the body.
How many spermatids are produced by each primary spermatocyte?
· 4 sperm
What is the acrosome cap?
· Encapsulates the head of the sperm and has enzymes that facilitate the fertilization of egg
What is the difference between spermatogenesis and spermiogenesis? What events occur during each of these, and where does each take place?
· Spermatogenesis: Occur in sertoli cells of testes, actual cell forms
· Spermiogenesis: maturation of sperm cell, addition of cap, tail formation, DNA elongates, etc. Occurs in Epididymis
Where does sperm maturation occur?
What is the difference between the corpus spongiosum and corpora cavernosa?
· corpora cavernosa: creates erection
· corpus spongiosum: surrounds urethra
What is the hypothalamic pulse generator?
· The hypothalalmic pulse generator is what causes the periodic release of GnRH from the hypothalamus, which acts on the anterior pituitary to release LH and FSH.
What is the role of LH and FSH in the male reproductive system?
· LH: doesn’t directly stimulate gamete formation-> Stimulates endocrine cells, stimulates steroid and peptide hormones, stimulates gamete formation
· FSH: Directly stimulates gamete production via Sertoli cell second messengers
Why are the testes located outside the body cavity in the scrotal sac?
· Testes away from body help with spermatogenesis
What is the pampiniform plexus and what does it do?
· The pampiniform plexus is a network of many small veins found in the human male spermatic cord. It is formed by the union of multiple spermatic veins from the back of the testis and tributaries from the epididymis. In addition to functioning as a venous return system, it also functions as a heat exchanger to control temperature in the scrotum.
What is the cremaster muscle and what does it do?
· The cremaster muscle is a muscle of the testes and spermatic cord, and it functions to raise and lower the testes to regulate their temperature.
What would be the effect of giving high doses of exogenous testosterone on the male reproductive structures?
· Testes will shrink
What happens if the testes do not descend properly into the scrotal sac?
· This is a disorder known as cryptorchidism and it occurs in 1-3% of newborn males. Most descend over time on their own, but if left undescended into puberty they will become sterile and unable to produce sperm.
What are the vas deferens?
· Tube that carry sperm from testes
What is the blood-testes barrier and what does it do?
· The blood-testes barrier, formed by sertoli cells and their tight junctions, functions much like the blood brain barrier to keep the capillaries here impermeable and to restrict the movement of molecules between the two compartments.
What is androgen-binding protein and why is it important?
· Androgen-binding protein, or ABP, is a product of Sertoli cells that is secreted into the lumen of seminiferous tubules where it binds to testosterone. This bound testosterone is unable to diffuse out of the lumen.
What do activin and inhibin do?
· Activins are peptides that stimulate FSH secretion. Inhibins do the exact opposite in that they inhibit FSH secretion.
What is the difference between emission and ejaculation?
· Emission is the phase where sperm moves from the testes to the prostatic urethra. Ejaculation is where sperm goes from the prostatic urethra to the outside of the body.
What division of the NS is active during erection? During ejaculation?
· During an erection the parasympathetic nervous system is in control, both opening smooth muscle and allowing blood to fill the spongy tissue. During ejaculation, sympathetic nervous system takes over.
How do the testes keep a high testosterone environment and why is this important?
· They keep the environment high using ABP to keep testosterone from diffusing. This is crucial because testosterone is needed for spermatogenesis.
What are the 3 phases of the uterine cycle & what changes occur during each?
1)proliferative phase: functionalis is thin, only stratum basale and base of glands, Estrogen stimulates gland rebuilding, spiral arteries lengthen and glands straighten and narrow (2)ovarian luteal phase: Progest & est levels elevated, endometrium thickens, glands grow, spiral arteries elongate, inc vascularity in the functionalis (3) menstrual phase: involution of the corpus luteum, arteries constrict, outer functional layer breaks down, Estrogen dec, functional layer sheds. Blood loss
In general, what changes occur to the stroma, spiral arteries, and uterine glands when estrogen levels are elevated? Where does this estrogen come from? What happens to the uterine structures if estrogen levels suddenly fall? What might cause such a rapid decline in estrogen levels?
The stroma proliferates, the spiral arteries lengthen, and uterine glands straighten and narrow. This estrogen comes from the follicle. The opposite happens to the structures when levels fall. The spiral arteries constrict, the stroma gets smaller, the functional layer sheds. The rapid decrease in estrogen levels can be caused by the dying of the corpus luteum.
What hormonal events occur during these cycles? (female)
LH sees a major peak before ovulation and FSH sees a small peak here too. Inhibin and estrogen see large peaks before ovulation as well. Estrogen, inhibin, and progesterone especially see high levels during the luteal phase of the ovarian cycle.
How do ovarian cycles relate to uterine cycles?
Menses and proliferative phase lead right up to ovulation, where the follicle is still in contact with the egg. The luteal phase coincides with the secretory phase because of the lack of an egg yet the secretion of the hormones.
How is the structure of the ovary different from that of the testis?
The ovaries are located inside the body, whereas the testes are outside of the body. The ovaries also contain all of the eggs they will ever need. The pathway to the uterus is relative short.
At what stage of meiosis is the oocyte from birth until just before ovulation?
The oocyte is arrested in prophase 1 until right before ovulation where it completes meiosis 1.
What are the layers of the endometrium and which one undergoes cyclic changes associated with the uterine cycle?
The endometrium has two layers, the stratum basale and the stratum functionale. The stratum functionale is the top layer and it undergoes cyclic changes associated with the uterine cycle due to estrogen levels.
What is the corpus luteum and what is its function? For each primary oocyte, how many mature ova are produced?
The corpus luteum is the remains of the collapsed follicle and the residual follicular and thecal cells. It functions to continue to secrete estrogen and progesterone after ovulation. For each primary oocyte, exactly one mature ovum is produced.
At what stage of meiosis is the primordial follicle? When does meiosis I complete during oogenesis? Meiosis II?
It is left in prophase one until it becomes ready to release as an adult. Meiosis 1 is completed shortly before ovulation in the female. Meiosis 2 is completed after the egg is fertilized (if it is fertilized).
What is an ectopic pregnancy and why is it potentially dangerous?
Ectopic pregnancy happens when a fertilized egg plants itself in the body outside of the uterus.
What is the zona pellucida? Corona radiata?
The zona pellucide is a glycoprotein coat that protects the ovum. The corona radiate are the loosely connected granulosa cells on the outside of an egg.
What are granulosa cells? Thecal cells? What do each of these do?
Granulosa cells are stimulated by FSH and they convert androgens to estrogens. Thecal cells are stimulated by LH and they secrete androgens.
What cells produce ovarian estrogens?
That would be granulosa cells. They receive androgens from the theca interna cells and convert it to estrogen.
What are the functions of the theca interna and theca externa cells?
Interna are the cells that produce and secrete androgens in the follicle and theca externa cells are those of the smooth muscle that help in ejecting the egg during ovulation.
What is a polar body?
A polar body is the part of the primary oocyte that breaks away from the egg. The polar body contains the second half of the 23 duplicated chromosomes and will eventually disintegrate.
What hormonal events occur prior to ovulation? What hormonal event triggers or induces ovulation?
Just before ovulation, high levels of estrongen along with rising levels of progesterone, enhance the pituitary responsiveness to GnRH. This increases LH production, causing the LH surge. This causes the final step of oocyte maturation which causes the oocyte to mature into an egg and a polar body. The LH peak induces ovulation.
What events occur during ovulation that help to expel the oocyte from the ovary?
The mature follicle secretes collagenase, which dissolves collagen. The follicular cell begins to break down, causing an inflammatory action that causes leukocytes to secrete prostaglandins. This may cause smooth muscle walls to contract and rupture the follicle at its weakest point. Antrial fluid spurts out of the follicle, sweeping the egg into the fallopian tube.
Where does the oocyte go after it is released during ovulation?
It exits the ovary and enters the fallopian tubes to head towards the uterus.
What is hCG and what structure produces it?
HCG is human chorionic gonadotropin, a peptide hormone that is secreted by chorionic villi and developing placenta. It is structurally related to LH and binds to LH structures. Under the influence of hCG, the corpus luteum keeps producing progesterone to keep the endometrium intact. A second function of it is stimulation of testosterone production by the developing testes in male fetuses.
What changes occur in the vagina and cervical mucus during the cycle?
Estrogen stimulates the cornification of the epithelium, and cervical mucus thins around the time of ovulation to facilitate the penetration by sperm and fertilization.
What effects do estrogen, progesterone, oxytocin, and prolactin have on the mammary gland?
Estrogen is what causes the breasts and mammary glands to grow during puberty and pregnancy. Progesterone converts the duct epithelium into a secretory structure. Prolactin form the anterior pituitary stimulates the secretion of milk. Oxytocin from the posterior pituitary causes what is known as the let down reflex, which allows the ejection of milk from the glands.
Where does fertilization normally occur? Implantation?
Fertilization usually occurs in the fallopian tubes, and implantation usually occurs on the lining of the uterus.
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