Mast cells secrete histamine (induces vasodilation, increases permeability of capillaries to bring in defensive proteins and antibodies, leads to local edema, redness, pain, and warmth) and cytokines (proteins that regulate immune cells)
Specific immune response may be triggered (antibodies produced)
What causes a fever? Describe the process of a fever.
A fever is generated in reponse to continued inflammation
Monocytes and macrophages release endogenous pyrogen in response to bacterial molecules
Endogenous pyrogen causes the hypothalamus to raise the body temperature set point (increasing body temperature)
This response is thought to help fight infections
What is an antigen?
Molecules or parts of molecules that stimulate adaptive immune response by lymphocytes (chemicals that lymphocytes recognize as being foreign)
Describe lymphocyte “creation” and types / where they are produced for the adaptive immune system.
Lymphocytes produced in bone marrow
Undergo several developmental stages
Colonize the thymus, lymph nodes, and spleen (multiplication of lymphocytes)
B-Lymphocytes “produced” in bone marrow
T-Lymphocytes “produced” in the thymus
What are the primary lymph organs?
Thymus and bone marrow
What is an antibody? Describe it and its functions (detailed).
The location of respiration (diffusion of O2 and CO2)
~300 million / lung in human adults
Diffusion promoted by increased surface area from alveoli (~100’ x 76’) and the short distance for diffusion (alveolar squamous cell, basement membrane, capillary squamous cell [~2 μm])
Intra-alveolar air pressure varies based on the size of the thoracic cavity
What are the thoracic cavity, diaphragm, and mediastinum?
Diaphragm – dome shaped muscle that separates the thoracic cavity (upper) from the abdominal cavity (lower)
Thoracic cavity – the upper area of the peritoneal cavity
Mediastinum – The central area of the peritoneal cavity containing the heart and trachea
What is the pleural membrane? Name its substructures.
The two-layered membrane that surrounds the lungs.
The parietal pleura lines the interior of the thoracic wall
The visceral pleura lines the surface of the lungs
The intrapleural space (pleural cavity) exists between the layers
Describe the intrapleural space in detail
The region between the parietal and visceral pleura
Filled with intrapleural fluid
Intrapleural pressure kept below atmospheric pressure, creating a slight vacuum
This vacuum adheres the lung surface to the surface of the thoracic cavity
Describe the intrapleural space vacuum in detail. How does it relate to lung expansion? Lung tissue has elastic recoil and tends to shrink
Thoracic wall recoil tends to expand
This generates a vacuum in the intrapleural space (pressure in intrapleural space < atmosphere)
This causes the lung to adhere to the thoracic wall
Changing the volume of the thoracic cavity changes lung volume
The vacuum also prevents lung collapse
What is pneumothorax? Why does it occur?
a collapsed lung which does not subsequently inflate
It is caused when the chest wall is opened (eg punctured), preventing the intrapleural space vacuum. As such the punctured lung no longer adheres to the thoracic wall, and the intra-alveolar air pressure equilibrates with atmospheric pressure.
What drives the movement of air in the lungs?
Pressure differences between atmospheric pressure and intra-alveolar pressure
Changing the size of the thoracic cavity (thus lung volume) changes intra-alveolar pressure. Atmospheric pressure remains constant.
What is atmospheric pressure? Its typical units? Physiological value?
The pressure exerted by the weight of air in the atmosphere
~760 mmHg (1 atm)
Physiologically considered “0” for comparison to intra-alveolar and intra-pleural pressure (negative creates a vacuum (inhalation) and positive creates a pressure (exhalation))
Describe intra-alveolar pressure, physiological value during normal breathing, and what occurs.
The pressure inside the alveoli
Changes from -3 (inhalation) to +3 (exhalation) during normal breathing
Summarize Boyle’s Law. How does this relate to breathing?
The pressure of gas is inversely proportional to its volume
Increased lung volume = decreased intra-alveolar pressure = air flows in
Decreased lung volume = increased intra-alveolar pressure = air flows out
Describe the influence of surface tension on ventilation.
Surface tension is created by the formation of H-bonds between water molecules
Surface tension within alveoli should be so that they collapse, however they have surfactant which lowers the surface tension
Describe surfactant in detail
protein + phospholipid – nonpolar
Secreted by Type II alveolar cells late in fetal life [no need for inflated lungs in the watery womb]
Premature infants may suffer from Respiratory distress syndrome (a lack of surfactant) which causes increased surface tension and thus an increased force is needed to inflate the lungs.
Describe the mechanics of lung ventilation (inspiration).
Contraction of the diaphragm (flattening) increases thoracic volume
Enlarged thoracic cavity results in expanded lung volume (intrapleural vacuum)
Expanded lung volume results in decreased intra-alveolar pressure (-3)
Air moves into the lungs (pressure gradient)
Describe the mechanics of lung ventilation (expiration).
Relaxation (convexing) of the diaphragm decreases thoracic volume
Smaller thoracic cavity results in decreased lung volume (elasticity/intrapleural vacuum)
Decreased lung volume results in increased intra-alveolar pressure (+3)
Air moves out of the lungs (pressure gradient)
What is spirometry? Difference between “volume” and “capacity?”
Measurements of breathing
Volume: a single measurement
Capacity: the sum of multiple volumes
What are the 4 primary lung volumes? (spirometry)
Tidal volume (TV): volume of air entering and leaving lungs in a single unforced breath
Inspiratory reserve volume (IRV): additional volume of air that can be maximally inspired beyond the tidal volume by forced inspiration
Expiratory reserve volume (ERV): additional volume of air that can be maximally expired beyond tidal volume by forced expiration
Residual volume (RV): volume of air still in lungs following forced maximum expiration
What are the 2 primary lung capacities?
Total lung capacity: Amount of air in lungs at the end of a maximal inspiration (sum of all 4 lung volumes)
Vital capacity: Maximum amount of air that can move out of lungs after a person inhales as deeply as possible (sum of TV, IRV, and ERV)
What are the three air-flow disorders (no descriptions)?
Restrictive disorders, obstructive disorders, and Chronic Obstructive Pulmonary Diseases (COPD)
Parietal cells: secrete hydrochloric acid, intrinsic factor (necessary for B12 absorption, B12 needed for erythropoesis)
Chief cells: secrete pepsinogen (a precursor to pepsin)
Enteroendocrine and secretory cells: Histamine and Gastrin (stimulate parietal cells), Ghrelin-secreting cells (hunger related)
Describe stomach acid secretion in detail
Parietal cells secrete H+ into the gastric lumen using active transport (H+ / K+ ATPase)
Cl- follows H+ from cells into the lumen
HCl used to denature ingested proteins, activate pepsinogen, create acidic pH for pepsin action, and destroy bacteria
HCl secretion stimulated by Histamine and Gastrin
Describe the activation of pepsinogen
Pepsinogen secreted by chief cells into the lumen
Low pH of gastric juice activates pepsinogen (-> pepsin)
Pepsin digests pepsinogen into pepsin (+ feedback)
Pepsin function: digest proteins into shorter polypeptides
Describe the three phases regarding gastric function
Cephalic phase: regulation of stomach by the brain via CN X, stimulates gastrin and histamine secretion in response to stimuli associated with food and anticipation of food
Gastric phase: arrival of food in stomach, amino acids and short polypeptides (not full proteins) stimulate pepsinogen, gastric, histamine, and HCl secretion
Intestinal phase: Arrival of chyme in small intestine stimulates neural reflex that inhibits gastric motility and secretion, fats in chyme stimulate secretion of hormones from the intestine that slow stomach function (allows more time for fat digestion in intestine)
Describe the small intestine
~3m long in living adults
Duodenum: receives chyme (stomach), bile (liver), pancreatic juice (pancreas)
Large surface area due to Plicae circularis (macroscopic circular folds in mucosa, similar to rugae), villi (microscopic fingerlike projections, contain capillaries and central lacteal for absorption), and microvilli (electron-microscopic “brush border” on surface of mucosal cells)
What are brush-border enzymes? Describe them and give examples?
Enzymes bound to epithelial cell membranes (microvilli)
Digest disaccharides, small peptides, etc (finish digestion started in stomach)
Include sucrase and lactase
Describe small intestine motility and its regulation
Peristalsis: propels chyme through the small intestine
Segmentation: mixes chyme with digestive secretions (major form of motility)
Intestinal contractions occur due to pacemaker potentials in smooth muscles
Main function: storage of undigested material (feces)
Enormous number of symbiotic bacteria in colon (probiotics will increase this number)
Functions of symbiotic bacteria in large intestine
Synthesize short chain fatty acids (fuel, aid in absorption)
Inhibit pathogenic bacteria
Describe the organization of the liver and delivery of blood (general)
Consists of hepatocytes organized into hepatic plates/cords (2 cells thick) separated by sinusoids (fenestrated capillaries)
Grouped into liver lobules
Blood delivered to liver lobules from the hepatic artery (oxygenated) and hepatic portal vein (deoxygenated, nutrient rich)
Describe blood flow through the liver. (How does the liver perform its tasks)
Blood enters periphery of liver lobules, flows through sinusoids
Sinusoids are fenestrated, leaky, and lack basement membrane
Allow passage of proteins and fats (into and out of hepatocytes)
Kupffer cells (macrophages) phagocytize, cleanse blood, remove old rbc’s
Blood drains out of the lobule via central vein that empties into the hepatic vein
Describe bile secretion from the liver.
Bile secreted into bile caniliculi from hepatocytes (flows from center toward periphery of liver lobules)
Bile caniliculi drain into bile ducts
Bile ducts drain into gall bladder, where bile is stored
Gall bladder transports to bile small intestine when needed
Describe the liver functions
Bile production: Converted from cholesterol for excretion, Bile salts emulsify fats, smaller droplets allow lipase to digest fats into fatty acids,
Bilirubin secreted into bile, derived from heme of the hemoglobin of destroyed RBCs, broken down bilirubin colors feces brown. A small amount is taken up by the small intestine and filtered by the kidney colorin urine yellow.
Detoxification of blood: Degradation of waste, hormones, drugs, etc by hepatocytes, phagocytosis by kupferr cells
Regulation of blood glucose: remove excess glucose from blood and convert it to glycogen (insulin), can secrete glucose into the blood when needed (glucagon)
Metabolism of lipids: converts cholesterol into bile salts and excretes it from the body, produces ketone bodies from fatty acids (provides fuel).
Excess ketone bodies can cause ketacidosis (associated with uncontrolled type I diabetes) hyperventilation to compensate
Synthesizes plasma proteins: albumin, clotting factors, and carrier proteins from nonpolar materials
High blood concentration of bilirubin leading to a “yellow” appearance
Caused by blockage of bilirubin excretion from gallstones, excessive RBC breakdown, liver damage
In a newborn can be caused by the slow breakdown of fetal hemoglobin (HbF), exposure to blue light expedites breakdown
Associated with liver disease or cirrhosis
Decreased blood osmolarity leads to buildup of fluid in the peritoneum (“beer belly”)
Describe the functions of the pancreas (re: digestion) + enzymes
Produces pancreatic juice (consists of bicarbonate to neutralize stomach acidity, and various enzymes…)
Pancreatic amylase – breaks down starch, Trypsin and other proteases (not pepsin) – break down polypeptides, Pancreatic lipase – digests triglycerides, phospholipases, nucleases, etc
Pancreatic juice travels through the pancreatic duct and enters the duodenum through the duodenal papilla, along with bile
How are enzymes secreted by the pancreas? Describe the specifics.
Pancreatic juice secreted by exocrine tissue in the pancreatic acini (not islets)
Cells secrete enzymes principally in the form of zymogens (inactive enzymes)
Zymogens are activated in the small intestine
Enterokinase (a brush border enzyme) converts trypsinogen into trypsin
Trypsin converts other zymogens into active enzymes
Describe the hormone regulation of Pancreatic Juice and bile secretion.
All are released FROM the small intestine
Hormones that inhibit the stomach are released when chyme enters the duodenum through the pyloric sphincter, this slows the flow of chyme to allow time for digestion
Secretin: stimulated by drop in pH below 4.5 (from acidic chyme), stimulates secretion of bicarbonate into the pancreatic juice, stimulates secretion of bile from the liver (alkaline)
Cholecystokinin (CCK): Stimulated by fat and protein content in chyme, stimulates digestive enzyme secretion into pancreatic juice, stimulates bile secretion from the liver and contraction of the gall bladder (more bile release)
CCK receptors in the hypothalamus (arcuate nucleus) give a feeling of satiety (negative feedback)
Describe carbohydrate digestion and absorption in detail
Amylase secreted in saliva AND pancreatic juice break starch into smaller carbohydrates (NOT monosaccharides)
Small carbohydrates are digested into monosaccharides by brush border enzymes (small intestine)
Monosaccharides are absorbed into the mucosa
Transported into blood, enter hepatic portal system
Used for metabolism OR stored as glycogen
Protein digestion and absorption in detail
Pepsin in the stomach cleaves proteins into smaller polypeptides
Pancreatic enzymes (trypsin) and brush border enzymes digest polypeptides into amino acids or small peptides (small intestine)
Small peptides and amino acids are transported into the mucosa
Small peptides broken into amino acids inside mucosal cells
Transferred into blood, enter hepatic portal system
AA taken up by cells and used for protein synthesis
Lipid Digestion and absorption in detail
Chyme mixed with bile in duodenum – lipids in chyme interact with bile salts, form emulsification droplets which prevent the lipids from aggregated into large droplets
Pancreatic lipases break emulsified fat into free fatty acids and monoglycerides
Fatty acids and monoglycerides are absorbed by the epithelium
Triglycerides are reformed in epithelial cells
Newly reformed triglycerides are combine with protein to form chylomicrons
Chylomicrons released via exocytosis, enter central lacteal of villus (lymph vessels have large pores)
Transported through the lymphatic system
Enters blood through thoracic duct at left subclavian vein
Fatty acids used as fuel or stored as triglycerides
What are the major factors for caloric expenditure of the body?
Basal metabolic rate (BMR): ~60% of calories used
Adaptive Thermogenesis: Energy expended to maintain body temperature and digest/absorb food
What happens to BMR when dieting? Why?
Body mass homeostasis (set point) achieved when caloric intake balances caloric expenditure
Homeostasis will slow BMR when dieting to maintain
Describe the arcuate nucleus and all of its influences
Regulates hunger and feeding behavior (hunger inhibiting neurons AND hunger stimulating neurons)
Arcuate nucleus influenced by….
Other brain areas: smell, vision, suggestion, emotions, nucleus accumbans etc
Ghrelin: secreted when stomach is empty (from stomach), stimulates hunger
CCK: reduces appetite (released when small intestine is filled with chyme)
Satiety factors (eg Leptin): suppresses hunger and elevates metabolic rate (released in response to increasing storage of fat in adipocytes, from adipose tissue)
Insulin: acts as a satiety factor (released from beta cells of Pancreas in response to increased blood glucose)
nucleus accumbans: Pleasure center of the brain
Describe the two phases of sexual reproduction (overview)
1. Production of gametes (sperm and ova)
produced by gonads (testes or ovaries)
Haploid (n, 23 chromosomes) – unique to gametes
2. Fertilization- Sperm and egg fuse to form a zygote
Zygote is diploid (2n, 46 chromosomes) – 22 pair autosomal chromosomes, one pair of sex chromosomes
Reproductive differences between males and females (gamete production, sex steroid release, and duration of reproductive life)
Gamete production: Ova released intermittently and in small numbers (1/month). Mature sperm are produced continuously and in massive numbers (~30 million/day)
Sex steroid release (endocrine): female hormones have cyclical release. Testosterone released continuously.
Duration of reproductive life: Both sexes begin at puberty, female ends during middle age (menopause). Male potential continues throughout life.
General function of the testis including specific compartments (and their functions)
General functions: produce sperm, produce testosterone
Seminferous tubules: site of spermatogenesis (sperm production)