Exam #4 Review Outline

Urinary System

• Functions of the Urinary System in Maintaining Homeostasis of Blood:

  • pH balance: Regulates blood pH by excreting hydrogen ions and reabsorbing bicarbonate.

  • Water balance: Controls blood volume and osmolarity by adjusting water reabsorption.

  • Electrolyte concentrations: Maintains proper levels of sodium, potassium, calcium, and other electrolytes.

  • Nutrient conservation: Prevents loss of glucose and amino acids by reabsorbing them.

  • Waste excretion (major waste products): Eliminates urea, creatinine, and other metabolic wastes.

  • Amino acid catabolism: Involved in the breakdown and processing of amino acids.

• Filtration in Renal Corpuscle:

  • Filtration barriers and diameters of afferent vs. efferent arterioles facilitate filtration: The glomerular filtration membrane includes the fenestrated endothelium, the basement membrane, and the podocytes. Afferent arterioles have larger diameters than efferent arterioles, increasing hydrostatic pressure and filtration rate.

• Calculations:

  • Net filtration pressure (NFP): NFP = GBHP - (CHP + BCOP), where GBHP is glomerular blood hydrostatic pressure, CHP is capsular hydrostatic pressure, and BCOP is blood colloid osmotic pressure.

  • Glomerular filtration rate (GFR): The volume of filtrate formed per minute by both kidneys. Normal GFR is approximately 125 mL/min.

• Control Mechanisms of Glomerular Filtration:

  • Autoregulation: Maintains a stable GFR despite changes in blood pressure.

  • Hormone regulation:

    • Renin-angiotensin-aldosterone system (RAAS): Increases blood pressure and sodium reabsorption.

    • Natriuretic peptides: Decrease blood pressure by increasing sodium and water excretion.

  • Autonomic regulation: Sympathetic stimulation constricts afferent arterioles, reducing GFR.

• Concepts in Renal Function:

  • Renal threshold: The plasma concentration at which a substance begins to appear in the urine.

  • Transport maximum: The maximum rate at which a substance can be reabsorbed.

  • Milliosmoles and their interpretation: Measure of the concentration of solute particles in a solution, influencing water movement in the kidneys. Normal range is 280-300 mOsm/L.

• Nephron and Collecting Ducts (CD):

  • Specialized functions of regions: Proximal convoluted tubule (PCT) for reabsorption, loop of Henle for creating concentration gradient, distal convoluted tubule (DCT) for hormone-regulated reabsorption and secretion, and collecting duct for final water reabsorption.

  • Varied histology related to functions: PCT has microvilli for increased surface area, loop of Henle has thin segments for water permeability, and DCT and CD have hormone-sensitive cells.

• Counter-Current Mechanisms:

  • Counter-current multiplication: Creates a concentration gradient in the medulla by the loop of Henle.

  • Counter-current exchange: Maintains the concentration gradient by the vasa recta.

• Processes:

  • Filtration: Movement of fluid and solutes from glomerulus to Bowman's capsule.

  • Secretion: Movement of substances from blood into the filtrate.

  • Reabsorption: Movement of substances from filtrate back into the blood.

• Hormonal Control:

  • Water and solute reabsorption in distal convoluted tubule and collecting duct: ADH increases water reabsorption, aldosterone increases sodium reabsorption and potassium secretion, and natriuretic peptides decrease sodium reabsorption.

• Urine Pathway:

  • From collecting ducts to excretion: Collecting ducts, renal papilla, minor calyx, major calyx, renal pelvis, ureter, urinary bladder, urethra, and external urethral orifice.

  • All collecting, storage, and transporting structures: Includes the renal calyces, renal pelvis, ureters, urinary bladder, and urethra.

• Excretory Organs:

  • Histology related to function: Ureters have transitional epithelium, bladder has detrusor muscle, and urethra varies with location (transitional to stratified squamous).

• Micturition Reflex:

  • Involuntary control mechanisms: Stretch receptors in the bladder wall trigger spinal reflexes that cause bladder contraction and relaxation of the internal urethral sphincter.

  • Voluntary control mechanisms: Cerebral cortex controls the external urethral sphincter, allowing voluntary urination.

• Age-Related Changes:

  • Affecting urinary excretion: Decreased GFR, reduced bladder capacity, and weakened urinary sphincters.

Electrolyte, Fluid, and Acid-Base Balance

• Body Water Percentage and Compartments:

  • Percentage of water in the human body: Approximately 60% in males and 50% in females.

  • Volume differences between intracellular (ICF) and extracellular fluids (ECF): ICF is about 2/3 of total body water, while ECF is about 1/3.

  • Major sub-compartments of ECF: plasma and interstitial fluid: Plasma is the fluid component of blood, while interstitial fluid surrounds cells.

• Major Ions:

  • Major cations and anions of the ICF and ECF: ICF: K^+, Mg^{2+}, HPO4^{2-}, proteins. ECF: Na^+, Cl^-, HCO3^-.

• Solid Components:

  • Relative abundance of major solid components: Proteins, lipids, carbohydrates, and minerals.

• Hormonal Regulation:

  • ADH: Increases water reabsorption in the kidneys.

  • Renin-angiotensin-aldosterone system: Increases sodium and water reabsorption, and potassium secretion.

  • Natriuretic hormones regulate fluid and electrolyte balance: Promote sodium and water excretion.

• Water Balance Homeostasis:

  • Maintenance between ICF and ECF when fluid is gained or lost: Water shifts between compartments to maintain osmotic balance.

• Sources and Elimination of Body Water:

  • Relative contribution of the sources of body water: Ingestion, metabolic synthesis.

  • Methods of elimination: Urine, feces, sweat, and insensible perspiration.

• Edema:

  • Definition and causes: Accumulation of excess fluid in interstitial spaces due to increased capillary hydrostatic pressure, decreased capillary osmotic pressure, increased capillary permeability, or impaired lymphatic drainage.

• Ion Homeostasis:

  • Sodium, potassium, and calcium homeostasis when ions are gained or lost: Regulated by hormones and renal function.

  • Deleterious effects of electrolyte imbalances, especially calcium and potassium: Hyperkalemia or hypokalemia can cause cardiac arrhythmias; hypercalcemia or hypocalcemia affects nerve and muscle function.

• Physiological Roles of Electrolytes:

  • Sodium: Maintains ECF volume, nerve and muscle function.

  • Potassium: Maintains ICF volume, nerve and muscle function.

  • Calcium: Bone structure, muscle contraction, nerve function, blood clotting.

  • Magnesium: Enzyme cofactor, muscle and nerve function.

  • Phosphorus: Bone structure, ATP production, nucleic acid structure.

  • Chloride: Maintains ECF volume, acid-base balance.

• Definitions:

  • Acid: A substance that donates hydrogen ions (H^+

  • Base: A substance that accepts hydrogen ions.

  • pH: A measure of hydrogen ion concentration; pH = -log[H^+].

  • Salt: An ionic compound formed from the reaction of an acid and a base.

  • Buffer: A substance that resists changes in pH.

• Classes of Acids:

  • Three classes of acids in the body: Volatile acids (e.g., carbonic acid), fixed acids (e.g., sulfuric acid), and organic acids (e.g., lactic acid).

• Buffering Systems:

  • Carbonic acid-bicarbonate buffering system: CO2 + H2O !\rightleftharpoons H2CO3 !\rightleftharpoons H^+ + HCO_3^-.

  • Protein buffering system: Amino acids can act as both acids and bases.

  • Phosphate buffering systems: Effective in ICF, where phosphate concentrations are high.

    • Fluid compartment where each system is most effective: Carbonic acid-bicarbonate in ECF, proteins in ICF and ECF, and phosphates in ICF.

• Acid-Base Disturbances:

  • Examples of acid-base disturbances of blood pH, PCO2, and/or HCO3^-:

    • Acute respiratory acidosis: Increased PCO_2, decreased pH.

    • Respiratory alkalosis: Decreased PCO_2, increased pH.

    • Metabolic acidosis: Decreased HCO_3^-, decreased pH.

    • Metabolic alkalosis: Increased HCO_3^-, increased pH.

    • Effects of renal or respiratory compensation on each disturbance: Renal compensation adjusts HCO3^- levels, while respiratory compensation adjusts CO2 levels.

• Aging Effects:

  • Effects of aging on fluid, electrolyte, and acid-base balance: Decreased renal function, reduced thirst sensation, and increased risk of dehydration.

Digestive System

• Major Functions:

  • Major functions of the digestive tract: Ingestion, mechanical processing, digestion, secretion, absorption, and excretion.

• Control Mechanisms:

  • Local control mechanisms: Enteric nervous system.

  • Neural control mechanisms: Autonomic nervous system.

  • Hormonal control mechanisms:

    • Peristalsis: Waves of muscle contraction that move food along the digestive tract.

    • Segmentation: Mixing movements that break food into smaller pieces.

• Oral Cavity:

  • Functions of organs:

    • Saliva: function and main components: Moistens food, begins starch digestion with amylase, and contains lysozyme for antibacterial action.

    • Control of salivation: Parasympathetic stimulation increases salivation.

    • Tooth: function of parts: Enamel protects the tooth, dentin provides structure, and pulp contains nerves and blood vessels.

    • Dental succession: Primary teeth are replaced by permanent teeth.

    • Cause of tooth decay: Bacteria metabolize sugars, producing acids that erode enamel.

• Esophagus:

  • Histology related to food transport function: Stratified squamous epithelium protects against abrasion.

• Deglutition:

  • Process and control of swallowing: Voluntary, pharyngeal, and esophageal phases, controlled by the swallowing center in the medulla oblongata.

• Stomach:

  • Anatomy related to digestion:

    • Secretory cells: Parietal cells, chief cells, mucous cells, and G cells.

    • Secretory products: HCl, pepsinogen, mucus, and gastrin.

    • Effects of their products: HCl activates pepsin, pepsin digests proteins, mucus protects the stomach lining, and gastrin stimulates HCl secretion.

• HCl Formation and Secretion:

  • Formation and secretion of HCl: Parietal cells use carbonic anhydrase to form H^+ and HCO_3^-. The H^+ is pumped into the stomach lumen.

  • Functions of HCl: Activates pepsin, denatures proteins, and kills bacteria.

• Stomach Protection:

  • How the stomach protects itself from acid: Mucus layer, tight junctions between epithelial cells, and rapid cell turnover.

• Gastric Secretion Regulation:

  • Cephalic phase: Stimulated by sight, smell, taste, or thought of food.

  • Gastric phase: Stimulated by stomach distension and increased pH.

  • Intestinal phase: Stimulated by chyme entering the duodenum.

• Reflexes:

  • Gastroenteric reflex: Stimulates intestinal motility and secretion.

  • Gastroileal reflex: Stimulates ileal motility and relaxation of the ileocecal valve.

• Small Intestines:

  • Structural and functional characteristics of the three regions:

    • Location of most absorption: Jejunum.

    • Secretion of digestive enzymes, bicarbonate, and mucus: Enterocytes secrete enzymes, Brunner's glands secrete bicarbonate, and goblet cells secrete mucus.

    • Vitamin B12 absorption: Ileum.

• Pancreas:

  • Major exocrine secretory components and their function: Acinar cells secrete pancreatic enzymes, and duct cells secrete bicarbonate.

• Liver:

  • Microanatomy: portal triads, sinusoids, Kupffer cells (liver macrophages), hepatocytes, and central veins

  • Suitability for metabolic and hematological regulation: Hepatocytes perform metabolic functions, Kupffer cells remove pathogens, and sinusoids facilitate exchange between blood and hepatocytes.

• Bile:

  • Synthesis: Hepatocytes.

  • Storage: Gallbladder.

  • Function: Emulsifies fats for digestion.

  • Recycling (enterohepatic circulation): Bile salts are reabsorbed in the ileum and returned to the liver.

  • Location of these processes: Synthesis in the liver, storage in the gallbladder, emulsification in the small intestine, and reabsorption in the ileum.

• Duodenal Hormones:

  • Gastrin: Stimulates gastric acid secretion.

  • Secretin: Stimulates bicarbonate secretion from the pancreas.

  • Gastric inhibitory peptide: Inhibits gastric motility and secretion.

  • Cholecystokinin: Stimulates bile release from the gallbladder and enzyme secretion from the pancreas.

  • Vasoactive intestinal peptide: Relaxes smooth muscle in the digestive tract.

• Large Intestines:

  • Specialized functions: Water absorption, electrolyte absorption, and vitamin synthesis.

  • Mass movements: Strong peristaltic contractions that move feces toward the rectum.

  • Defecation reflex: Stimulated by rectal distension.

• Microbiota:

  • Relative distribution and roles in the gastrointestinal tract: Ferments undigested carbohydrates, synthesizes vitamins, and inhibits pathogen growth.

• Comparison:

  • Structure and function of small vs. large intestine: Small intestine has villi and microvilli for absorption, while the large intestine has haustra for water absorption and storage of feces.

• Digestion and Absorption:

  • Carbohydrates: Broken down into monosaccharides.

  • Lipids: Broken down into fatty acids and glycerol.

  • Proteins: Broken down into amino acids.

    • Major enzymes involved: Amylase (carbohydrates), lipase (lipids), and protease (proteins).

    • How these nutrients are absorbed: Monosaccharides and amino acids are absorbed by active transport, while fatty acids and glycerol are absorbed by diffusion.

• Ion Absorption:

  • Mechanisms of ion absorption: Active transport and diffusion.

  • Major ions absorbed: Sodium, potassium, calcium, chloride, and bicarbonate.