Exam 3 (Chapters 24-27) Flashcards
What are the GI tract (aka, alimentary canal) organs?
Mouth, most of pharynx, esophagus, stomach, small intestine and large intestine.
What are the accessory digestive organs?
Teeth, tongue, salivary glands, liver, gallbladder and pancreas.
Organs of the Digestive System
Organs of the Digestive System
What are the six functions of the digestive system?
- Ingestion (taking in foods and liquids) 2. Secretion (of water, acid, buffers and enzymes into lumen) 3. Mixing and Propulsion (motility) 4. Digestion (mechanical digestion churns food; chemical digestion - hydrolysis) 5. Absorption (entrance of ingested and secreted liquids, ions and digestive products into blood or lymph) 6. Defecation (elimination of feces)
Layers of the GI Tract
Layers of the GI Tract
Neural Innervation of the GI Tract: Enteric Nervous System (ENS)
- Intrinsic set of nerves (“brain of gut”) - Neurons extending from esophagus to anus - Plexuses: myenteric plexus (GI tract motility) and submucosal plexus (controlling secretions)
Neural Innervation of the GI Tract: Autonomic Nervous System (ANS)
- Extrinsic set of nerves - Parasympathetic stimulation: increases secretion and activity by stimulating ENS. - Sympathetic stimulation: decreases secretions and activity by inhibiting ENS.
Peritoneal Folds
Peritoneal Folds
Deglutition (Swallowing)
Deglutition (Swallowing)
External and Internal Anatomy of the Stomach
External and Internal Anatomy of the Stomach
Mechanical Digestion in the Stomach
Mixing waves - gentle, rippling peristaltic movements - creates chyme
Chemical Digestion in the Stomach: Salivary Amylase
Salivary amylase: - digestion continues until inactivated by acidic gastric juice
Chemical Digestion in the Stomach: Lingual Lipase
Lingual lipase: - acidic gastric juice activates lingual lipase - digest triglycerides into fatty acids and diglycerides
Chemical Digestion in the Stomach: HCl
HCl - Parietal cells secrete H+ and Cl- separately but net effect is HCl - Kills many microbes, denatures proteins
Chemical Digestion in the Stomach: Pepsin
Pepsin - Secreted by chief cells - Secreted as inactive pepsinogen - Digests proteins
Chemical Digestion in the Stomach: Gastric Lipase
Gastric Lipase - Splits triglycerides into fatty acids and monoglycerides
Absorption in the Stomach
- Small amount of nutrient absorption - Some water, ions, short chain fatty acids, certain drugs (aspirin) and alcohol.
Relation of the Pancreas to the Liver, Gallbladder, and Duodenum
Relation of the Pancreas to the Liver, Gallbladder, and Duodenum
The Liver
The Liver
Gallbladder
- A pear-shaped sac in the posterior surface of the liver - Contraction of smooth muscle fibers eject contents of gall bladder into cystic duct - Functions to store and concentrate bile produced by the liver until it is needed in the small intestine - Absorbs water and ions to concentrate bile up to ten-fold
Other Crucial Functions of the Liver
- Carbohydrate, lipid and protein metabolism - Processing of drugs and hormones - Storage - Phagocytosis - Activation of Vitamin D
Anatomy of the Small Intestine
Anatomy of the Small Intestine
Chemical Digestion in the Small Intestine: Carbohydrates
- pancreatic amylase - ɑ-dextrinase of the brush border acts on ɑ-dextrins - common disaccharides are not acted on until the small intestine—sucrose, maltose and lactose
Chemical Digestion in the Small Intestine: Proteins
- trypsin, chymotrypsin, carboxypeptidase, and elastase from pancreas - aminopeptidase and dipeptidase in brush border
Daily Volumes of Fluid Ingested, Secreted, Absorbed and Excreted from the GI tract
Daily Volumes of Fluid Ingested, Secreted, Absorbed and Excreted from the GI tract
Daily Volumes of Fluid Ingested, Secreted, Absorbed and Excreted from the GI Tract: Ingested and Secreted
- Saliva (1 liter) - Ingestion of liquids (2.3 liters) - Gastric juice (2 liters) - Bile (1 liter) - Pancreatic juice (2 liters) - Intestinal juice (1 liter) Total ingested and secreted = 9.3 liters
Daily Volumes of Fluid Ingested, Secreted, Absorbed and Excreted from the GI Tract: Absorbed
- Small intestine (8.3 liters) - Large intestine (0.9 liters) Total absorbed = 9.2 liters
Daily Volumes of Fluid Ingested, Secreted, Absorbed and Excreted from the GI Tract: Excreted
- Excreted in feces (0.1 liter)
Anatomy of the Large Intestine
Anatomy of the Large Intestine
Anatomy of the Large Intestine (continued)
Anatomy of the Large Intestine (continued)
Metabollism
All chemical reactions occuring in the body.
Catabolism
Catabolism = breaking down of complex molecules.
Catabolism is exergonic—it produces more energy than it consumes.
Anabolism
Anabolism = combine simple molecules to create complex molecules
Anabolism is endergonic = consuming more energy than it produces
Adenosine Triphosphate (ATP)
ATP = “energy currency”
ADP + P + energy ⇔ ATP
Energy Transfer
Energy transfer is accomoplished through oxidation-reduction (REDOX) reactions.
Oxidation
- Removal of electrons
- Decrease in potential energy
- Dehydrogenation (removal of hydrogens)
- Liberated H is transferred by coenzymes
- EXAMPLES:
- Nicotinamide adenine dinucleotide (NAD)
- Flavin adenine dinucleotide (FAD)
- Glucose is commonly oxidized to yield energy
Overview of Cellular Respiration
Overview of Cellular Respiration
Glycolysis Reactions
Glycolysis Reactions
The Krebs Cycle is also known as…
The Krebs Cycle is also known as the citric acid cycle
Where does the Krebs cycle occur?
In the matrix of the mitochondria
What is the Krebs cycle?
A series of REDOX reactions.
What are the important processes and steps of the Krebs cycle?
- 2 decarboxylation reactions release CO2
- Reduced coenzymes (NADH and FADH2) are the most important outcome
- One molecule of ATP generated by substrate-level phosphorylation
Chemiosmosis
Chemiosmosis
Glycogenesis and Glycogenolysis
Glycogenesis and Glycogenolysis
Lipoproteins - How are they categorized and named?
Lipoprotiens are categorized and named according to density (ratio of lipids to proteins)
Lipoproteins - Chylomicrons
- Forms in small intestine mucosal epithelial cells
- Transport dietary lipids to adipose tissue
Lipoproteins - Very Low-Density Lipoproteins (VLDLs)
- Forms in hepatocytes
- Transport endogenous lipids to adipocytes
Low-Density Lipoproteins (LDLs)
- “bad” cholesteral
- Carry 75% of total cholesterol in blood
- Deliver to body cells for repair and synthesis
- Can deposit cholesterol in fatty plaques.
High-Density Lipoproteins (HDLs)
- “good” cholesteral
- Remove excess cholesterol from body cells and blood
- Deliver to liver for elimination
Lipid catabolism (lipolysis)
- Triglycerides split into glycerol and fatty acids
- Must be done in muscle, liver, and adipose tissue to oxidise fatty acids
- Enhanced by epinephrine and norepinephrine
Lipid anabolism (lipogenesis)
- Liver cells and adipose cells can synthesize lipids from glucose or amino acids
- Occurs when more calories are consumed than needed for ATP production.
Postabsorptive State Reactions
Glucose related reactions: After the glucose from a meal has been absorbed, eventually the supply of glucose available in the blood becomes depleted. How can the body produce new glucose?
- Breakdown of liver glycogen (our major source of stored carbohydrates)
- Lipolysis (breaking down lipids)
- Note: the fatty acid chains cannot become glucose, but the glycerol portion of a triglyceride can)
- Gluconeogenesis using lactic acid
- Gluconeogenesis using amino acids
Postabsorptive State Reactions - Non-glucose related reactions
- Oxidation of fatty acids
- Oxidation of lactic acid
- Oxidation of amino acids
- Breakdown of muscle glycogen
Body Temperature Homeostasis - Overview
Despite wide fluctuations in environmental temperatures, homeostatic mechanisms maintain normal range for internal body temperature.
Body Temperature Homeostasis - What is the body’s core temperature and shell temperature?
Core temperature = 37ºC (or 98.6ºF)
vs.
Shell temperature = 1-6ºC lower than core temp.
Body Temperature Homeostasis - Heat Production Methods
-
Exercise
- A fit individual can increase heat production by 15-20 times greater than resting metabolic rate through exercise.
- Hormones
-
Sympathetic Nervous System
- Release of epinephrine and norepinephrine (via sympethetic activation - e.g., caused by a stressor or during exercise) increases metabolic rate.
- Fever
-
Ingestion of food
- Food induced thermogenesis can be anywhere between 10-20% above basal metabolic rate. The highest gain (20%) is after a protein-rich meal; the lowest (10%) is after a carbohydrate-rich meal.
- Young age
Heat Loss - Conduction
Heat lost through conduction(e.g., to clothing surrounding the body), at rest, is only about 3% of the body’s heat.
Heat Loss - Convection
- Convection = movement of a gas or liquid (e.g., the body moving air)
- Typically we lose about 15% of our heat to the surrounding air
Heat Loss - Radiation
- Radiation = transfer of heat in the form of infrared rays (think night vision goggles/thermal imaging?)
- A resting person in a 70ºF room loses about 60% of their heat through radiation **at rest.
- This is our most important way of losing heat.
Heat Loss - Evaporation
- Evaporation of sweat from the surface of the skin
- At rest, a person only loses about 20% of their heat* *through evaporation.
- During exercise, this becomes the most important method of heat loss (cooling).
Heat and Energy Balance - Hypothalamic thermostat is…
- Located in the preoptic area
- It is the heat-losing (cooling) center and heat-promoting (warming) center.
Vitamins are…?
Organic nutrients required in small amounts to maintain growth and normal metabolism.
Vitamins do not…?
Vitamins do not provide energy or serve as building materials for the body.
Most vitamins are…?
Coenzymes.
Most vitamins cannot be…?
Most vitamins cannot be synthesized by the body.
How is vitamin K produced?
Vitamin K is produced by bacteria in the GI tract.
Some vitamins can be assembled from…what?
Some vitamins can be assembled from provitamins.
Provitamin: a precursor of a vitamin, convertible into the vitamin in an organism
EXAMPLE: ergosterol is a provitamin of vitamin D
Vitamins are placed in one of two groups, depending on whether they are…?
Vitamins are grouped based on whether they are…
fat-soluble (A, D, E, K)
or
water-soluble (several B vitamins and vitamin C)
What functions does the kidney perform?
-
Regulation of blood ionic concentration
- (most important ions = Na+, K+, Ca2+, Cl- and HPO42- [phosphate ions])
-
Regulation of blood pH
- (via secretion of H+ into urine and conservation of HCO3- [bicarbonate ions], which are an important buffer of H+ in the blood. Normal blood pH is 7.4 +/- 0.2)
-
Regulation of blood volume
- (inc. BV = inc. in BP; kidneys inc. or dec. BV by conserving or eliminating water in the urine)
- Regulation of blood pressure
- Also:
- Maintenance of blood osmolarity
- Production of hormones (Calcitrol [the active form of vitamin D] and erythropoietin)
- Regulation of blood glucose level
- Excretion of wastes from metabolic reactions and foreign substances (drugs or toxins)
Internal Anatomy of the Kidneys: Renal Cortex - superficial
- outer cortical zone
- inner juxtamedullary zone
- renal columns—portions of cortex that extend between renal pyramids
Internal Anatomy of the Kidneys: Renal Medulla - inner region
- several cone-shaped renal pyramids—base faces cortex and renal papilla points toward hilum
Internal Anatomy of the Kidneys: Renal Lobe
- renal pyramid; overyling cortex area and half of each adjacent renal column
Internal Anatomy of the Kidneys (A)
Internal Anatomy of the Kidneys (A)
Internal Anatomy of the Kidneys (B)
Internal Anatomy of the Kidneys (B)
Cortical Nephrons - Overview
- Cortical nephrons comprise 80-85% of nephrons
- Renal corpuscle located in outer portion of cortex and short loops of Henle extend only into outer region of medulla
Cortical Nephrons - Flow
Cortical Nephrons - Flow
Juxtamedullary Nephrons - Overview
- Juxtamedullary nephrons comprise the other 15-20% of nephrons
- Renal corpuscle is deep in cortex and long loops of Henle extend deep into medulla
- Receive blood from peritubular capillaries and vasa recta
- Ascending limb has thick and thin regions
- Enable kidneys to secrete either very dilute or very concentrated urine.
Juxtamedullary Nephrons - Flow
Juxtamedullary Nephrons - Flow
Histology of a Renal Corpuscle
Histology of a Renal Corpuscle
Tubular Reabsorption
Reabsorption is the return of most of the filtered water and many solutes to the bloodstream.
- About 99% of filtered water is reabsorbed
- Proximal convoluted tubule cells make largest contribution
- Solutes are reabsorbed by both active and passive processes
Tubular Secretion
Tubular secretion is the transfer of material from blood into tubular fluid.
- Secretion of H+ helps control blood pH
- Secretion helps eliminate substances from the body
Reabsorption Routes and Transport Mechanisms
Reabsorption Routes and Transport Mechanisms
Reabsorption in the Loop of Henle: Chemical composition of tubular fluid is…?
The chemical composition of tubular fluid is quite different from filtrate. Glucose, amino acids and other nutrients have been reabsorbed.
Reabsorption in the Loop of Henle: Osmolarity is…?
Osmolarity is still close to that of blood. Reabsorption of water (osmosis) and solutes are balanced.
Reabsorption in the Loop of Henle: For the first time, water is…?
For the first time, reabsorption of water is NOT automatically coupled to reabsorption of solutes. There is independent regulation of both volume and osmolarity of body fluids.
Reabsorption in the Loop of Henle: Symporters
Na+-K+-2Cl- symporters function in Na+ and Cl- reabsorption.
Reabsorption in the Loop of Henle: Little or no water is reabsorbed…where?
Little or no water is reabsorbed in the ascending limb. Osmolarity decreases progressively towards the end of the ascending limb.
Hormonal Regulation of Tubular Reabsorption and Secretion:
Renin-Angiotensin-Aldosterone System (RAAS)
- Renin is released when blood volume and pressure decrease.
- Renin converts angiotensinogen to angiotensin I
- ACE converts angiotensin I to angiotensin II
Hormonal Regulation of Tubular Reabsorption and Secretion:
Angiotensin II affects renal physiology by…?
Angiotensin II affects renal physiology by:
- Decreasing GFR
- Enhancing reabsorption of Na+, Cl-and water in the PCT
- Stimulates Aldosterone release by adrenal cortex
- Stimulates principal cells in collecting ducts to reabsorb more Na+ and Cl- and secrete more K+
Summary of Filtration, Reabsorption and Secretion in the Nephron Collecting Duct
Summary of Filtration, Reabsorption and Secretion in the Nephron Collecting Duct
Evaluation of Kidney Function:
Blood Tests
- Blood urea nitrogen (BUN) - measures blood nitrogen that is part of the urea resulting from catabloism and deamination of amino acids.
- Plasma creatinine results from catabolism of creatine phosphate in skeletal muscle.
Evaluation of Kidney Function:
Renal Plasma Clearance
- Volume of blood cleared of a substance per unit time.
- High renal plasma clearance indicates efficient exretion of a substancec into urine.
- PAH administered intravenously to measure renal plasma flow
- More useful in diagnosis of kidney problems than above tests.
Ureters, Urinary Bladder and Urethra
Ureters, Urinary Bladder and Urethra
Body Fluid Compartments
Body Fluid Compartments
The body can gain water by…
The body can gain water by:
- Ingestion of liquids and moist foods (2300 mL/day)
- Metabolic synthesis of water during cellular respiration (200 mL/day)
The body can lose water through…
The body can lose water through:
- Kidneys (1500 mL/day)
- Evaporation from skin (600 mL/day)
- Exhalation from Lungs (300 mL/day)
- Feces (100 mL/day)
Series of Events in Water Intoxication
Series of Events in Water Intoxication
Intracellular Fluid (ICF) vs. Extracellular Fluid (ECF)
- ECF’s most abundant cation is Na+, anion is Cl-
- ICF most abundant cation is K+, anions are proteins and phosphates (HPO42-)
- Na+/K+ pumps play a major role in keeping K+ high inside cells and Na+ high outside cells.
Sodium (Na+)
- Most abundant ion in ECF
- 90% of extracellular cations
- Plays pivotal role in fluid and electrolyte balance because it accounts for almost half of the osmolarity of ECF
- Level in blood is controlled by:
- Aldosterone—increases renal absorption
- ADH—if sodium is too low, ADH release stops
- Atrial Natriuretic Peptide (ANP)—increases renal excretion
Bicarbonate (HCO3-)
- 2nd most prevalent extracellular anion
- Concentration increases in blood passing through systemic capillaries picking up carbon dioxide
- Carbon dioxide combines with water to form carbonic acid which dissociates
- HCO3- drops in pulmonary capillaries when carbon dioxide is exhaled
- Chloride shift helps maintain correct balance of anions in ECF and ICF
- Kidneys are main regulators of blood HCO3-
- Can form and release HCO3- when blood level is low or excrete excess to the the urine if blood level is high.
Calcium (Ca2+)
Most abundant mineral in body:
- 98% of calcium in adults is in skeleton and teeth
- In body fluids, main an extracellular cation
- Plays important roles in blood clotting, neurotransmitter release, muscle tone, and excitability of nervous and muscle tissue.
Concentration is regulated by parathyroid hormone:
- Stimulates osteoclasts to release calcium from bone—resorption
- Also enhances reabsorption from glomerular filtrate
- Increases production of calcitrol to increase absorption from GI tract
Acid-Base Balance
- Keeping H+ concentration (pH) of body fluids at an appropriate level is a major homeostatic challenge.
- 3D shape of proteins sensitive to pH
- Diets with large amounts of proteins produce more acids than bases, which acidifies blood
- Several mechanisms help maintain pH of arterial blood between 7.35 and 7.45
- Buffer systems
- Exhalation of CO2
- Kidney excretion of H+
Acid-Base Imbalances
The normal pH range of arterial blood is between 7.35 and 7.45
- Acidosis = blood pH below 7.35 (acidic)
- Alkalosis = blood pH above 7.45 (basic)
What are the major physiological effects of acid-base imbalances?
- Acidosis—results in depression of synaptic transmission in CNS
- Alkalosis—results in overexcitability of CNS and peripheral nerves
Respiratory Acidosis
Respiratory Acidosis:
- Abnormally high PCO2 in systemic arterial blood
- Cause is inadequate exhalation of CO2
- Any condition that decreases movement of CO2 out—emphysema, pulmonary edema, airway obstruction
- Kidneys can help raise blood pH
- Goal is to increase exhalation of CO2 - ventilation therapy
Respiratory Alkalosis
Respiratory Alkalosis:
- Abnormally low PCO2 in systemic arterial blood
- Cause is hyperventilation due to oxygen deficiency from high altitude or pulmonary disease, stroke, or severe anxiety.
- Renal compensation can help.
- One simple treatment: breathe into a paper bag for a short time
Metabolic Acidosis
Metabolic Acidosis:
- Abnormally low HCO3- in systemic arterial blood
- Loss of HCO3- from severe diarrhea or renal dysfunction
- Accumulation of an acid other than carbonic acid—ketosis
- Failure of kidneys to excrete H+ from metabolism of dietary proteins
- Hyperventilation can help
- Administer IV sodium bicarbonate and correct cause of acidosis
Metabolic Alkalosis
Metabolic Alkalosis:
- Abnormally high HCO3- in systemic arterial blood
- Nonrespiratory loss of acid - vomiting of acidic stomach contents, gastric suctioning
- Excessive intake of alkaline drugs (antacids)
- Use of certain diuretics
- Severe dehydration
- Hypoventilation can help
- Give fluid solutions to correct Cl-, K+
