Unit 4- Complete Study Guide PDF

Urinary System- Study Guide Structures of Urinary System: ● Kidneys: filter blood and convert the filtrate into urine ● Ureters: urine is transported by the ureters from the kidneys to the urinary bladder ● Urinary bladder: an expandable, muscular sac that stores as much as 1 liter of urine ● Ureth...

Urinary System- Study Guide Structures of Urinary System: ● Kidneys: filter blood and convert the filtrate into urine ● Ureters: urine is transported by the ureters from the kidneys to the urinary bladder ● Urinary bladder: an expandable, muscular sac that stores as much as 1 liter of urine ● Urethra: urine eliminated through urethra Functions: ● Elimination of metabolic wastes ● Regulation of ion levels ION= Elecrolytes * E.g., Na+, K+, Ca2+ ● Regulation of acid-base balance (Blood PH) * Alters levels of H+ and HCO3 ● Regulation of blood pressure ● Elimination of biologically active molecules * hormones, drugs Location of Kidneys the left kidney: in between the level of the T12 and L3 vertebrae the right kidney: about 2 centimeters inferior to the left kidney to accommodate the large size of the liver Concave medial border, hilum ● Where vessels, nerves, ureter connect to kidney Anterior Posterior 4 tissue layers that surround and support the kidneys ● Fibrous capsule: GIVES IT ITS SHAPE ○ Directly adhered to external surface of kidney ○ Dense irregular CT ○ Maintains kidney’s shape ○ Protects it from trauma ○ Prevents pathogen penetration ● Perinephric fat: CUSHION & SUPPORT ○ Adipose Connective Tissue external to fibrous capsule ○ Cushions and supports kidney ● Renal fascia: HELPS CONNECT KIDNEY TO WALL ○ External to perinephric fat ○ Dense irregular CT ○ Anchors kidney to ○ surrounding structures ● Paranephric fat: CUSHION ○ Outermost layer surrounding kidney ○ Adipose CT ○ Anchors kidney to surrounding structures Regions and components of kidney: Renal Cortex: outermost region of the kidney. Renal Columns: project into the medulla and subdivide it into renal pyramids.- Renal Pyramids: striped structures within the medulla. Medulla: inner portion of the kidney.Corticomedullary Junction: where the outer edge of the medulla meets the cortex. Renal Papilla: located at the narrow/inner part of the renal pyramids. Each funnel-shaped minor calyx is associated with a pyramid and merge into larger major calyx which then merges to form the renal pelvis which then drains into the collecting duct. The Autonomic innervation of the kidney ● ● Sympathetic nerves ○ extend from the T10-T12 segments of the spinal cord to the blood vessels of the kidney. ○ These nerves innervate the afferent and efferent arterioles, which are responsible for regulating blood flow in and out of the glomerulus ○ Decreases urine production Parasympathe4c nerves from CN X (Vagus) ○ Specific effects not known ○ extends to the juxtaglomerular apparatus, which is involved in regulating renal blood pressure and fluid balance ○ This sympathetic input plays a role in modulating renal vascular resistance and adjusting glomerular filtration rate based on physiological needs. "Sympathetic nerves originating from the T10-T12 segments of the spinal cord provide innervation to the blood vessels of the kidney, including the afferent and efferent arterioles, as well as the juxtaglomerular apparatus" Renal Corpuscle and its components ● ● The renal corpuscle is located in the renal cortex and consists of the glomerulus and the glomerular capsule. The glomerulus is a network of capillary loops where blood enters through the afferent arteriole and exits through the efferent arteriole. The glomerular capsule has two layers: ● ● a visceral layer that covers the glomerular capillaries directly, and an external parietal layer. Between the two layers of the glomerular capsule is a capsular space that receives filtrate. Components of a Renal Tubule Proximal convoluted tubule (PCT): ● First region of the renal tubule ● Composed of simple cuboidal epithelium with tall microvilli ● Microvilli increase reabsorption capacity Nephron loop: ● Begins at the sharp end of the PCT ● Includes a descending limb and ascending limb ● Portions classified as thick or thin based on epithelium lining (thick, thin, thin, thick) Distal convoluted tubule (DCT): ● Starts at the end of the nephron loop and extends to the collecting duct ● Made up of simple cuboidal epithelium ● Contains much shorter microvilli Types of nephrons and the functional difference between them The cortical nephrons are located with their corpuscles near the top edge of the cortex and have a short loop that barely touches the medulla. 85% of nephrons are cortical. The juxtamedullary nephrons corpuscle lies near where the renal medulla and renal cortex meet. Its loop extends deep into the renal medulla. These nephrons are important in establishing salt concentration gradient in ISF, which allows regulation of urine concentration by ADH. Collecting tubules & Collecting ducts ● ● ● ● Each kidney contains numerous collecting tubules and larger collecting ducts. Tubules and ducts project towards the renal papilla. Collecting ducts empty into papillary ducts within the renal papilla. Epithelial cells in tubules start as cuboidal-shaped and then transition to columnar shape in the collecting ducts. Functions of the two types of specialized epithelial cells found within collecting tubules and ducts principal cells: have cellular receptors to bind both aldosterone (released from the adrenal cortex) and antidiuretic hormone (released from the posterior pituitary) intercalated cells (types A and B): specialized epithelial cells that help regulate urine pH and blood pH Location & structure of the Juxtaglomerular Apparatus ● The juxtaglomerular apparatus is where the DCT (Distal convoluted tubule) of a nephron makes contact with afferent arteriole of the same nephron, this is important in regulating filtration formation and systemic BP. ● Contract when stimulated by stretch or sympathetic stimulation Synthesize, store and release Renin The granular cells are modified smooth muscle cells of the afferent arteriole located near the entrance to renal corpuscle. One function is to contract when stimulated by stretch or sympathetic division. They also synthesize, stores and releases renin enzyme which is required to make angiotensin I. The macula densa cells are modified cells in the DCT where they make contact with the granular cells only on the tubular side next to the afferent arteriole, and they are narrow and tall. These cells detect changes in NaCl concentration of fluid in the lumen of DCT. They also signal granular cells to release the renin. Blood Supply to the Kidneys (Arteries that supply the kidney, in sequence from largest to smallest) Renal artery segmental arteries interlobar arteries arcuate arteries interlobular arteries afferent arterioles glomerulus efferent arterioles peritubular capillaries/vasa recta interlobular veins arcuate veins interlobar veins renal vein. Veins through which blood leaves the kidney in sequence from smallest to largest. cortical radiate veins arcuate veins interlobar veins renal vein There are three types of capillaries in the kidneys, namely afferent arterioles, efferent arterioles, and vasa recta. The afferent arteriole delivers blood to the glomerulus, and that blood is then filtered into the glomerular capsule. Through the efferent arteriole the blood leaves the glomerulus, and flowing through the efferent arteriole it is no longer filtered. From the efferent arterioles, vasa recta are separate, and these are the capillaries through which blood flows. As blood flows through the vasa recta, there is an exchange of nutrients and gases. Capillary beds through which blood must pass in the kidney. Blood passes through afferent arteriole to glomerulus. After filtration, blood enters the second capillary bed of peritubular capillaries or vasa recta via the efferent arteriole. Peritubular capillaries are intertwined around proximal and distal convoluted tubules, primarily reside in cortex. Vasa recta capillaries are straight vessels associated with nephron loop, primarily reside in medulla Filtrate, Tubular fluid, and Urine Filtrate ● A filtrate is a fluid formed by filtering blood into the glomerulus ● Through the glomerular membrane, the blood filtrate enters the capsular space. ● Large molecules remain in the blood, which does not pass through the glomerular membrane. Tubular fluid ● formed in the tubules of the nephron ● is formed due to the exchange of gases and Nutrients from the filtrate that enters the tubules. Urine ● ● by collecting ducts, the kidneys leave the urine Urine is final when it leaves the collecting duct until it excretes from the body. Structures That Transport Fluids Through the Urinary System ( In order) 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. Capsular Space Proximal convoluted tubule Descending Limb of nephron loop Ascending limb of nephron loop Distal convoluted tubule Collecting tubules Collecting duct Papillary duct Minor Calyx Major Calyx Renal Pelvis Ureter Urinary Bladder Urethra Steps of Urine Formation 1. Glomerular Filtration- turning blood plasma into filtrate ● The movement of substances from the blood within the glomerulus into the capsular space ● separates some water and dissolved solutes from the blood plasma within glomerulus. ● H2O and solutes enter capsular space due to a pressure difference across the membrane. (this fluid is called filtrate) 2. Tubular Reabsorption ● The movement of substances from the tubular fluid back into the blood ● Tubular fluid moves by transport process (e.g. diffusion, active transport etc.) from the lumen of collecting tubules and ducts across their walls and return to blood through capillaries. ● Generally, all solutes and most waters are reabsorbed, excess solutes and H2O remain in the fluid. 3. Tubular secretion: ● The movement of substances from the blood into the tubular fluid ● movement of solutes by active transport out of the blood and into the tubular fluid. ● Materials are selectively moved into tubules to be eliminated. Glomerular Filtration Membrane Layers Endothelium of glomerulus allows plasma and its dissolved substances to be filtered while restricting passage of large structures, like formed elements Basement membrane of glomerulus restricts passage of large plasma proteins while allowing smaller substances to pass Visceral layer of glomerulus ● composed cells called podocytes, octopus-like cells, long "feet" that wrap around glomerular capillaries to support capillary wall. ● The "feet" are separated by thin filtration silts that are covered with membrane. One podocytes "feet" interlock with another to restrict the passage of most small proteins. Examples of substances that are freely filtered, that are not filtered, and that are filtered in a limited way. Freely filtered- Water, glucose, amino acids, ions, urea, some hormones etc can pass easily through a filtered membrane and become part of filtrate and have the same concentration as plasma. Not filtered- Formed elements (RBCs, WBCs etc) and large proteins cannot normally pass-through filtration membranes. Cannot become part of filtrate. Limited filtration- Intermediate sized proteins are generally not filtered. They are blocked either because of size or - charge since the membrane had a negative charge. Glomerular Hydrostatic Pressure (HPg) Pressures that oppose HPg (pushing back against) Blood colloid osmotic pressure (OPg) - Osmotic pressure exerted by dissolved solutes E.g., plasma proteins Capsular hydrosta@c pressure (HPc) (pushing back into capsule) - Pressure in glomerular capsule due to filtrate - Impedes movement of additional fluid Glomerular Filtration Rate and the factors that influence it Glomerular Filtration Rate (GFR) ● Rate at which the volume of Filtrate is formed ● Volume per unit of time (usually 1 min) ● Helps kidney control urine production based on physiologic conditions Influenced by: ● Increased blood volume and increased blood pressure will increase GFR. ● Constriction in the afferent arterioles going into the glomerulus and dilation of the efferent arterioles coming out of the glomerulus will decrease GFR Intrinsic and Extrinsic controls Intrinsic controls ● Intrinsic ability of kidney to maintain constant blood pressure and GFR ● Maintains in spite of changes in systemic arterial pressure ● Functions by two mechanisms: ○ Myogenic response ( Myo= Muscle)- within kidney ■ Contraction or relaxation of smooth muscle of afferent arteriole in response to stretch ■ Allows more blood into glomerulus ■ ■ ■ ■ ■ ■ ■ ■ ■ ○ E.g., Decreased blood pressure = less stretch of smooth muscle in arteriole Compensates for lower system pressure GFR remains normal With increased blood pressure, more stretch of smooth muscle in arteriole Vessels constrict Allows less blood into glomerulus Compensates for greater systemic pressure GFR remaining normal Example:Renal autoregulation, decrease in systemic blood pressure (when taking a nap), causes vasodilation of afferent arteriole, allowing more blood into glomerulus, which compensates for lower systemic blood pressure. Tubuloglomerular feedback mechanism- outside of kidney ■ “Backup” to myogenic mechanism response to increased blood pressure ■ If glomerular blood pressure increased: ● Amount of NaCl in tubular fluid also increased ● Detected by macula densa cells in juxtaglomerular apparatus ● Results in further vasoconstriction of afferent arteriole ● Example:Exercise, Activating sympathetic division for fight-or-flight response results in decrease in GFR due to vasoconstriction of afferent arteriole. Nerve signals sent to kidneys during exercise cause vasoconstriction in afferent and efferent arterioles, greatly reduces blood flow into glomerulus. Characteristics and conditions that affect tubular reabsorption and secretion Tubular reabsorption – Substances move from tubule into blood Peritubular capillary – Low hydrostatic pressure, high colloid osmotic pressure Transcellular transport – Movement of substances across and epithelial cell Paracellular transport – Movement of substances between epithelial cells Tubular secretion – Substances move from blood into tubule Substances for which reabsorption is regulated Na+, water, K+, HCO3- and Ca2+. Sodium, water, Potassium, Bicarbonate, and Calcium Reabsorption of sodium, potassium, calcium, and Phosphate Sodium Amount reabsorbed from tubular fluid can vary from 98-100%. ● It is reabsorbed along the entire length of the nephron tubule, collecting tubules and collecting ducts, majority (65%) reabsorbed in proximal convoluted tubule, 25% in nephron loop, 5% in DCT. ● Na+ moves down its concentration gradient across luminal membrane into tubular cell of PCT. ● Na+/K+ pumps move Na+ within tubular cell into interstitial fluid, Na+ concentration low in tubule cells. Na+ enter peritubular and vasa recta capillaries through intercellular clefts. Potassium Reabsorption depends upon movement of Na+. 1.Sodium is reabsorbed across luminal membrane. 2. Water follows Na+. 3. Concentration of the remaining solutes in the tubular fluid increases as water follows movement of Na+. 4. Potassium moves down it concentration gradient from tubular fluid into blood by paracellular route. 5. These conditions also allow passive reabsorption of other solutes, including other cations (Mg2+, Ca2+), phosphate ion, fatty acids, and urea. 10-20% of K+ in tubular fluid is reabsorbed in thick segment of nephron looop ascending limb by transcellular and paracellular transport. Calcium & Phosphate Amount excreted in urine is regulated by parathyroid hormone (PTH) influences blood levels of Ca2+ and PO4 1. PTH is released from the parathyroid gland in response to decreased blood calcium. 2. PTH inhibits phosphate reabsorption in proximal convoluted tubule, stimulates calcium reabsorption in distal convoluted tubule. Reabsorption of water, and compare how it is regulated by the actions of aldosterone and antidiuretic hormone ● ● ● ● ● Reabsorbed by paracellular transport between cells, by transcellular transport through specific water transport proteins - aquaporins. Movement of water out of proximal convoluted tubule follows Na+ by osmosis, referred to as obligatory water reabsorption. Water moves from descending limb of nephron loop into vasa recta. Aldosterone increases number of Na+/K+ pumps and Na+ channels in principal cells, increase Na+ and water reabsorption. Antidiuretic hormone (ADH) released from posterior pituitary gland when we are dehydrated. ADH binds to receptors of principal cells of collecting tubules and collecting ducts to increase migration of vesicles containing aquaporins to the luminal membrane.This provides additional channels for water reabsorption. Nitrogenous waste products, and their fate Urea, Uric Acid, and Creatinine. Urea and uric acid are reabsorbed and secreted. Creatinine is only secreted. Substances eliminated as waste products: Most secretion occurring in PCT ● ● ● Certain drugs E.g., penicillin, sulfonamides, aspirin Other metabolic wastes E.g., urobilin(causes yellow color in pee), hormone metabolites (estrogens, progestogens, androgens, cortisol and melatonin) Some hormones – Human chorionic gonadotropin (hCG), epinephrine Explain what is meant by the countercurrent multiplier that occurs within the nephron loop. ● ● ● ● involves nephron loop and helps establish gradient. Juxtamedullary nephrons are primarily involved Kidney countercurrent multiplication refers to the process in which energy is used to create an osmotic gradient that enables the reabsorption of water from the tubular fluid, so that urine can be concentrated. Countercurrent multiplication creates this gradient by actively moving sodium chloride from the tubular fluid into the interstitial space deep within the kidneys. Partially responsible for establishing salt concentration gradient within interstitial fluid. Countercurrent refers to tubular fluid's "reversing" its relative direction as ot moves first through descending limb then through ascending limb. Multiplier is positive feedback loop that increases the concentration of salts within interstitial fluid. Contribution of urea cycling to the concentration gradient. ● ● ● ● ● Recycled urea makes up one-half of the solutes in ISF (interstitial fluid) concentration gradient. Urea is removed in collecting ducts via urea uniporters. It diffuses back into tubular fluid at the ascending limb. DCT ( distal convoluted tubule)will not let urea leave, so when it reaches the collecting ducts it is removed there. Urea is cycled between collecting tubules and nephron loops. Summary of reabsorption and secretion • After filtration • Majority or most other substances reabsorbed or secreted • Nephron loop, vasa recta, and urea recycling • Responsible for establishing concentration gradient of interstitial fluid • Necessary for normal function of ADH • Regulation of specific substances • Hormonal controls • Urine • Composed of water, dissolved substances, waste products • Drained into renal sinus of kidney • Excreted by urinary tract Procedure for measuring the glomerular filtration rate to determine how well kidneys work: 1.Someone is injected with inulin which is freely filtered and is not reabsorbed nor secreted in the kidney. SO the amount of inulin in urine is equal to the amount that is filtered. Urine collected and measured for volume and concentration Plasma concentration of inulin measured at given time intervals Normal GFR 125 mL/min-Less than this indicates decrease in kidney function Renal plasma clearance Renal clearance of a substance refers to how quickly a particular substance is removed from the plasma by the kidney and excreted in urine.So something with a high renal clearance means that it will be quickly removed from the blood, and vice versa. Kidney Transplant Identify the substance that may be measured to estimate the glomerular filtration rate. If a substance (such as inulin) is NEITHER reabsorbed or secreted the RPC will be the same as GRF, but if its reabsorbed then the RPC will be lower than GFR. Due to fluid leaving. Substances that are BOTH reabsorbed and secreted will have a RPC higher than GRF because extra substances are secreted back into tubular fluid. Composition of Urine and its characteristics. • Product of Filtered and processed blood plasma • Sterile unless contaminated with microbes in kidney or urinary tract • Characteristics: composition, volume, pH, specific gravity, color and turbidity, smell • Composition • 95% water, 5% solutes • Salts, nitrogenous wastes, some hormones drugs, ketone bodies • Abnormal constituents –glucose, blood cells, proteins • Volume • Average 1 to 2 L per day • Variations due to fluid intake, blood pressure, temperature, diuretics,diabetes, other fluid Excretion • WE NEED Minimum of 0.5 L to eliminate wastes from body • Below 0.40, wastes will accumulate in blood Structure and Function of the Ureters ● ● ● ● Ureters are long fibromuscular tubes that transport urine from kidney to the urinary bladder. They originate at the renal pelvis and exit the hilum of the kidney and extend towards the base of the urinary bladder. Enter posterolateral wall of base of urinary bladder Wall contains three tunics (in to out): muscoa, muscularis, and adventita. Structure of the Urinary Bladder ● ● ● ● ● ● Urinary bladder is an expandable, muscular organ that serves as a reservoir for urine. In females the bladder is anteroinferior to the uterus and directly inferior to the vagina. Males the bladder is anterior to the rectum and superior to the prostate gland. This is a retroperitoneal organ and only the superior surface is covered with parietal peritoneum. When it is empty it resembles an inverted pyramid shape and when it is full it is oval shaped. Trigone are imaginary lines connecting ureter openings and urethra, and funnels to direct urine into urethra. Distinguishing characteristics of the female and male urethra. Female: Single function is to transport urine from the bladder to the outside. Inside lined with stratified squamous epithelium opens at external opening in female perineum. Shorter urethra Male: Passageway for urine and semen, longer than female urethra Three segments: prostatic urethra, membranous urethra, spongy urethra Conscious control over micturition: Starts from the cerebral cortex through the pudendal nerve. This causes relaxation of the external urethral sphincter which is facilitated by voluntary contraction of abdominal and expiratory muscles, and after emptying detrusor muscle relaxed,micturition reflex inhibited, and storage reflex activated. Chapter 25- Fluids, Electrolytes and Acid- Balance Body Fluids: ● There are large amounts of water in the body, in percentages ranging from 45% to 75%. ● The amount of water contained in the body depends on two factors, namely age and adiposity. ● With aging, the amount of water in the body decreases, so this percentage decreases. The percentage of water in the body increases when the amount of adipose connective tissue decreases, or when a person loses weight, and vice versa. Factors that influence the percentage of body fluid: Age: ● ● ● ● Infants—highest percentage of fluid Elderly—lowest percentage Children, young and middle-aged adults—in middle range Body fluid decreases with age ● Males have more skeletal muscle, so slightly higher % ● % decreases with increased body fat Determines susceptibility to fluid imbalance ● Individuals with lower percentage, at higher risk ● E.g., elderly at more risk than young adults Major body fluid compartments Specific extracellular fluids • Cerebrospinal fluid • Synovial joint fluid • Aqueous and vitreous humor of the eye • Fluids of inner ear • Serous fluids within body cavity Not typically subject to significant daily gains and losses Which ions are more prevalent in the intracellular Fluid? Which are more prevalent in the extracellular Fluid? potassium, magnesium, phosphate, and negatively charged proteins sodium and chloride as well as bicarbonate Define fluid balance. Fluid balance is an aspect of the homeostasis of organisms in which the amount of water in the organism needs to be controlled, via osmoregulation and behavior, such that the concentrations of electrolytes in the various body fluids are kept within healthy ranges. Sources of fluid intake Ingested/preformed water: water from food and drink in the GI tracts (2300 mL avg daily) Metabolic water: produced daily from aerobic cellular respiration and dehydration synthesis (200 mL/day) Causes of fluid imbalance Fluid imbalance occurs if fluid output does not equal fluid intake. Organized into five categories Volume depletion, volume excess, dehydration, hypotonic hydration, and fluid sequestration. Fluid imbalance with constant osmolarity • Occurs when isotonic fluid is lost or gained • Volume depletion • Occurs when isotonic fluid loss is greater than isotonic fluid gain • E.g., hemorrhage, severe burns, chronic vomiting, diarrhea,hyposecretion of aldosterone • Volume excess • Isotonic fluid gain is greater than isotonic fluid loss • Fluid intake normal but decreased fluid loss through kidneys • In both, no change in osmolarity • No net movement of water between compartments Fluid imbalance with changes in osmolarity Dehydration: Water loss greater than loss of solutes • Results from profuse sweating, diabetes, intake of alcohol,hyposecretion of antidiuretic hormone (ADH), insufficient water intake, overexposure to cold weather • Blood plasma becomes hypertonic • Water shifts from cells into interstitial fluid and blood plasma • Possible dehydration of body cells Fluid imbalance with changes in osmolarity (continued) • Hypotonic hydration: water gain or retention that is greater than solute gain or retention • Water intoxication • Can result from ADH hypersecretion • Usually from drinking large amount of plain water • Both Na+and water lost during sweating • Drinking water only replaces the water, not the solutes • Plasma becomes hypotonic • Fluid moving from blood plasma into interstitial fluid and into cells • Possible swelling of cells • Cerebral edema due to brain cells swelling • Convulsions, coma, and death in severe cases Fluid sequestration Total body fluid is normal, but distributed abnormally Examples: • Edema, puffiness with fluid accumulation in interstitial space • Ascites, accumulation of fluid within peritoneal cavity • Pericardial effusion, accumulation of fluid in pericardial cavity • Pleural effusion, accumulation of fluid in pleural cavity Hormones that are involved in regulating fluid output 1. Angiotensin II 2. Antidiuretic hormone ADH 3. Aldosterone - decreases urine output to increase blood vol. & pressure 4. Atrialnatriuretic peptide ANP - increases urine output to decrease blood vol. & pressure Electrolyte ● ● ● ● Role: Dissociate in solution to form cations and anions Ability of substances to conduct electrical current when dissolved Nonelectrolyte ● ● Molecules that do not dissociate in solution Most covalently bonded organic molecules Each with unique function and osmotic functions Concentration given as milliequivalents/L (mEq/L) Electrical charges in 1 L solution Six major electrolytes found in body fluids Identify the main location, functions, and the means of regulation for each of the common electrolytes Sodium Ion ( NA+) ● 99% ECF and 1% ICF, maintained by Na+ & K+ pumps ● principle cation in ECF, exerts greatest osmotic pressure ● regulated by aldosterone, ADH, & ANP ● most important in determining blood plasma osmolarity and regulating fluid balance ● imbalance above normal hypernatremia, below normal hyponatremia Chloride ion Cl-: ● most abundant in ECF ● regulated by aldosterone, ADH, and ANP Potassium ion K+: ● 98% ICF and 2% ECF ● exerts osmotic pressure ● required for neuromuscular activities and controlling heart rhythm ● regulated by aldosterone ● most lethal of electrolyte imbalance ● most K+ lost in urine Calcium ion CA2+ ● most abundant in teeth 99% ● needed for muscle contraction ● serves as secondary messenger ● participates in blood clotting Phosphate ion Po43 ● abundant in ICF ● 85% stored in icone and teeth as calcium phosphate ● component of DNA and RNA Magnesium Mg2+ ● primarily with in bone and cells ● second most abundant in ICF ● mportant in muscle relaxation ● participates in enzymatic reactions ● regulated through kidney Explain why Na+ is a critical electrolyte in the body The human body requires a small amount of sodium to conduct nerve impulses, contract and relax muscles, and maintain the proper balance of water and minerals.Sodium is one of the most important electrolytes because it is one of the two main cations (along with potassium) that influences the generation of resting and action membrane potential. Variables that influence K+ distribution Potassium distribution is altered in response to changes in blood plasma levels of K+, changes in H+ blood plasma concentration, and the presence of specific hormones. Angiotensin II formation Angiotensinogen is constantly inactive made enzyme that is made by the liver. Its activation is initiated by renin. This is released in response to low blood pressure, or stimulation by the sympathetic division. Primary effects of angiotensin II ● ● ● ● Can stimulate vasoconstriction of systemic blood vessels to increase resistance, which increases blood pressure. It also stimulates a decrease in urine output from the kidneys a result of lower filtration rate, by stimulating vasoconstriction of afferent arteriole. this helps maintain systemic blood volume and blood pressure. Stimulates the thirst center in the hypothalamus, which increases blood volume and blood pressure. Stimulates both the hypothalamus to activate posterior pituitary to release Adh and adrenal cortex to release aldosterone. Explain how release of antidiuretic hormone (ADH) occurs from the posterior pituitary. ● Is released in response to nerve signals from the hypothalamus. ● Is stimulated by angiotensin II binding to receptors on the hypothalamus which was due to low blood pressure. ● Sensory baroreceptors in the atria of the heart and carotid blood vessels stimulate hypothalamus and a decrease in this can be caused by low blood volume. ● ● This is only under critical conditions of blood loss. Hypothalamus chemoreceptors detect an increase in blood osmolarity, and is the primary stimulus for ADH release. Conditions that lead to aldosterone release ● Release of angiotensin II, ● decreased blood plasma levels of Na+, ● an increased blood plasma levels of K+ Describe the changes that occurs in response to binding of aldosterone by kidney cells ● Aldosterone binds to receptors on principal cells of the kidney. ● This binding causes cells to increase reabsorption and retention of Na+ and water. ● This hormone increases the number of Na+/K+ and Na+ channels so that more Na+ is reabsorbed from the filtrate. ● Water will follow the Na+. K+ excretion is normally increased except when there is low pH. ● As Na+ and K+ are reabsorbed H+ is excreted out of the blood, thus levels go up. ● Low blood pressure and changes in Na+ and K+ blood plasma levels cause aldosterone release. Describe the stimulus for the release of atrial natriuretic peptide (ANP) and its three actions ● The stimulus that causes ANP release is atrial dilation caused by high blood pressure and increased blood volume. ● The three basic functions of ANP are: ○ dilatation of systemic blood vessels ○ vasodilation of afferent arterioles and relaxation of mesangial cells ○ inhibition of sodium and water reabsorption in kidneys Explain the ways in which the effects of atrial natriuretic peptide differ from the effects of angiotensin II, ADH, and aldosterone ● ● ANP increases urine output, therefore, blood volume and systemic blood pressure decreases. ANP inhibits the release of renin, the action of angiotensin II, and the release of ADH and aldosterone, thus preventing the actions of these hormones. Categories of Acid ● ● Fixed acid is the metabolic acids produced from metabolic wastes, include lactic acid, ketoacids. ○ Fixed acid is regulated by the kidney through the reabsorption and elimination of HCO3- and H+ ○ Examples of fixed acids include lactic acid from glycolysis, phosphoric acid from nucleic acid metabolism, and ketoacids from metabolism of fat Volatile acid is a carbonic acid produced from the combination of CO2 and water in the presence of carbonic anhydrase.Referred to as “volatile” because it is produced from an expired or evaporated " gas". ○ Volatile acid is regulated by the respiratory system through the regulation of the respiratory rate Describe how the kidneys counteract increasing blood H+ To maintain acid-balance, excess H+ is eliminated by kidney tubules through the making and absorption of HCO3- and the excretion of H+ into the filtrate. Explain how the kidneys function in response to decreasing blood H+. ● When alkaline conditions are present the renal tubules will no longer reabsorb the HCO3-. ● It will secrete HCO3- from the blood into the filtrate while reabsorbing H+ in exchange through type B intercalated cells. Explain the normal relationship between breathing rate and acid-base balance ( Blood PH) Respiratory system regulates level of carbonic acid When the body is at rest: • CO2 normally eliminated from lungs at same rate produced During exercise: • CO2 , H+, and O2 Levels detected by chemoreceptors • Relayed to respiration center to alter breathing rate • Changes in CO2—most important variable • Carbonic acid levels dependent on CO2 levels Components of the protein buffering system. Composed of one or two types of molecules • Can bind and release H+ within a fraction of a second • Composed of a weak base and weak acid • Weak base can bind excess H+ • Weak acid can release H+ • Temporary and limited, until physiologic buffering systems can eliminate the excess acid or base • The three most important chemical buffering systems: 1. protein—within cells and the blood ● This buffering system is composed of proteins within cells and in the blood plasma. ● The amine group (-NH2) of amino acids acts as weak base to buffer acid. ● Carboxylic acid of amino acids acts as a weak acid to buffer base. ● Intracellular proteins, plasma proteins, and hemoglobin all perform as pH buffers. weak base+strong acid= weak acid/weak acid+strong base= weak base 2. phosphate—within cells ● The buffering system is found within the ICF is composed of hydrogen phosphate (weak base) and dihydrogen phosphate (weak acid) and serves as a buffering system for pH changes within cells. ● Like protein buffering either a strong acid buffered to produce a weak acid or a strong base buffered to produce a weak base. 3. bicarbonate—within ECF, particularly bloods ● Most important buffering system in ECF ● Composed of a weak base and weak acid • Weak base, bicarbonate (HCO3–) • Weak acid, carbonic acid (H2CO3) ● Buffering capacity—limitation in amount of acid or base that the chemical buffering systems can buffer Explain acid-base disturbance, compensation, and acid-base imbalance ● ● ● When the buffering capacity of the chemical buffering systems is exceeded and the physiologic buffering systems are required to intervene due to a change in blood pH, an acid-base disturbance is occurring. Compensation occurs when the body's buffering system returns the blood pH to normal. When the body's buffering systems are unable to return the blood pH to normal, the pH disturbance is called uncompensated and, should the pH change be continuous and persistent, it is called acid-base imbalance. Define respiratory acidosis, identify some of the causes of this type of acid-base disturbance, and explain how it occurs ● ● Respiratory acidosis occurs due to impaired elimination of CO2 by the respiratory system, causing arterial blood levels of P(CO2) to become elevated. Injury to the respiratory center maybe by trauma, disorders of the nerves or muscles involved with breathing, airway obstruction, or a decreased gas exchanged due to reduced respiratory surface area. Define respiratory alkalosis, identify some of the causes of this type of acid-base disturbance, and explain how it occurs ● Respiratory alkalosis occurs due to an increase in respiration. ● This can be due to hyperventilating from severe anxiety and the condition that someone isn't getting enough oxygen(Hypoxia) or an aspirin overdose (stimulates respiratory center). Explain how metabolic acid-base disturbances differ from respiratory acid-base Disturbances. Metabolic disorders of acid-base status differ from respiratory ones in that they are not caused by changes in the concentration of volatile acid (carbonic acid) but by changes in the concentration of bicarbonate ions, which arose as a result of a metabolic disorder. Metabolic disorders can be both acidosis and alkalosis. metabolic acidosis ● ● Metabolic acidosis occurs when blood levels of HCO3 decrease May be caused by increased production of metabolic acids, decreased the elimination of acid due to renal dysfunction, and increased elimination of HCO3- due to diarrhea. metabolic alkalosis ● ● Metabolic alkalosis occurs when HCO3blood levels increase. This may be caused by vomiting, increased acid loss due to overdose of diuretics, increased alkaline input. Renal and Respiratory Compensation ● ● ● Renal compensation in response to elevated H+ concentration results in increased excretion of H+, increased production and reabsorption of HCO3- and lower than normal urine pH. Respiratory compensation in response to metabolic acidosis results in increased expiration of CO2, showed by a lower than normal blood P(CO2) value. Respiratory compensation in response to metabolic alkalosis results in decreased expiration of CO2, showed by a high than normal blood P(CO2) value. Chapter 26- Digestive System Organs that make up the gastrointestinal (GI) tract. The GI tract organs form a continuous tube and are: 1. Oral cavity and Pharynx 2. Esophagus 3. Stomach 4. small intestine 5. large intestine 6. anus. In here food is broken down into smaller pieces and absorbed. Accessory digestive organs and structures involved in the digestive process Accessory organs help with food breakdown and include 1. teeth and tongue 2. Gallbladder 3. salivary glands 4. Liver 5. Pancreas. General functions of the digestive system Ingestion- intro if solids and liquids nutrients into the mouth. 1st step in the process of digesting and reabsorbing nutrients. Motility- Voluntary and involuntary muscle contractions for mixing and moving stuff in the GI tract Secretion- producing and releasing substances that facilitate digestion Digestion- the breakdown of ingested food into smaller pieces that can be absorbed. 1. Mechanical digestion is materials being physically broken down. 2.Chemical digestion involves enzymes that break chemical bonds. Absorption- membrane transport of digested molecules, vitamins, waster from GI to blood. Elimination- the expulsion of indigestible components that are not absorbed. General process of absorption. Digested substances are transported from the lumen of the GI tract through the epithelium. These substances only need to cross the epithelium of the mucosa through the membrane transport process to be absorbed into blood capillaries or lymphatic capillaries. Action of muscularis mucosae and muscularis tunic Muscularis mucosa: ● is composed of a thin layer of smooth muscle and it is located neighboring to the submucosal layer. ● The smooth muscle contractions are responsible for: • The release of mucosal secretions into the lumen. • Efficient absorption. Muscularis tunic is only for motility, mixing through GI tract and peristalsis ● Mixing involves muscular contraction of the muscularis layer which is responsible for promoting the mixing of substances in the GI tract. ● Propulsion involves the movement of substances across the lumen of the GI tract. General function of the enteric nervous system and autonomic nervous system in the regulation of the digestive system. Enteric nervous system (ENS) • Sensory and motor neurons within submucosal plexus and myenteric plexus • Innervates smooth muscle and glands of GI tract • Coordinates mixing and propulsion reflexes Autonomic Nervous System (ANS) • Parasympathetic innervation promotes GI tract activity • Sympathetic innervation opposes GI tract activity Enteric nervous system -ANS • Controls digestion independent of CNS • Sensory -Detects changes in tract wall and chemical makeup of lumen content • Motor – Changes blood flow and epithelial cell function • Thickened at several points to form a sphincter • Closes off the lumen • Controls movement of materials into next section of GI tract Reflexes that regulate the digestive system Nerve reflexes • Baroreceptors detect stretch in GI tract wall • Chemoreceptors monitor chemical contents in lumen • Reflexes (by ANS or ENS) are initiated in response to receptor input • Short reflex – local reflex, only involves ENS; coordinate small segments of GI tract • Long reflex – involves sensory input to CNS and autonomic motor output;coordinate GI tract motility, secretions, and accessory digestive organs List the major hormones that regulate the processes of digestion Several hormones participate in regulation of digestion • E.g., Gastrin, secretin, cholecystokinin, motilin Distinguish between intraperitoneal and retroperitoneal organs. Intraperitoneal organs • Organs completely surrounded by visceral peritoneum • Includes stomach, most of small intestine, parts of large intestine Retroperitoneal organs • Lie directly against posterior abdominal wall • Only anterolateral portions covered with peritoneum • Includes most of duodenum, the pancreas, ascending and descending colon, the rectum. Function of the mesentery, and describe the five individual mesenteries of the abdominopelvic cavity Mesentery: double layer of peritoneum that supports, suspends, and stabilizes GI tract organs. Sandwiched between the folds are vessels that supply the tract. Greater omentum: extends inferiorly like an apron from the inferolateral surface of the stomach and covers most of the ab. organs. Accumulates large amounts of adipose connective tissue thus referred to as the fatty apron insulating organs with fat storage. Lesser omentum: connects superomedial surface of the stomach and proximal end of the duodenum to the liver Falciform ligament: flat. thin, crescent shaped peritoneal fold that attaches the liver to the internal surface of the anterior abdominal wall Mesentery proper: Fan shaped fold of peritoneum that suspends most of the small intestine from the internal surface of the posterior abdominal wall Mesocolon: fold of the peritoneum that attaches the large intestine to the posterior abdominal wall. Several distinct sections depending on the part of the colon it suspends. Anatomic structures in the oral cavity 1) Vestibule/Buccal cavity: Space between gums/lips/cheeks 2) Oral cavity proper: lies central to the teeth Cheeks contain buccinator muscles that compress cheeks against teeth to hold solid materials in place during mastication. Palate: forms superior boundary/roof acts as a barrier to separate it from the nasal cavity. The anterior two thirds is hard while the posterior one third is soft and muscular. Uvula: elevates to close off posterior entrance during swallowing to prevent entering nasal region Fauces: opening between oral cavity and oropharynx Tongue: formed primarily from skeletal muscle. Papillae cover the superior surface of the tongue and for taste. Posteroinferiorly contain lymphatic clusters (lingual tonsil) attaches to floor via lingual frenulum. Involved in swallowing and speech production Most of the cavity is stratified squamous epithelium (nonkeratinized, keratined for lip lining, part of tongue, and some of the hard palate) Describe the structure and function of salivary glands and how the release of saliva is regulated Salivary glands • Produce saliva • Intrinsic salivary glands (within oral cavity) • Unicellular glands • Continuously release secretions independent of food • Contains lingual lipase, enzyme that begins digestion • Extrinsic salivary glands (outside of oral cavity) • Produce most saliva • Parotid, submandibular, and sublingual glands Parotid salivary glands, largest salivary glands • 25–30% of saliva • Infection of the parotid glands causes mumps • Submandibular salivary glands • Produces 60–70% of salliva • Sublingual salivary gland • Contribute only 3–5% of saliva Process of mastication Mechanical digestion requires coordinated activities of teeth, skeletal muscles in lips, tongue, cheeks, and jaws controlled by nuclei within the medulla oblongata and pons (mastication center). Reduces bulk to facilitate swallowing. Structure and development of the teeth Teeth - Also known as the dentition • Exposed crown and constricted neck • One or more roots, anchoring it to jaw • Fit tightly into dental alveoli, sockets within alveolar processes • Bound to processes by periodontal ligament • Gomphosis joint: roots, dental alveoli, periodontal ligament Deciduous and permanent teeth- Development • 20 Deciduous teeth • Erupt between 6 and 30 months • 32 Permanent teeth, replacing deciduous teeth • More anteriorly placed permanent teeth appearing first • Third molars, wisdom teeth, in late teens or 20s • May emerge partially or become impacted Anatomy of the pharynx and esophagus and their complementary activities in the process of swallowing. Gross anatomy of the pharynx • Funnel-shaped muscular passageway • Passageway for air and food/water • Lined with nonkeratinized stratified squamous epithelium • Protection against abrasion Gross anatomy of the esophagus • Esophagus: normally collapsed, tubular passageway • Passageway for food/water • Esophagus lined with nonkeratinized stratified squamous epithelium • Inferior region connecting to the stomach • Passes through opening in diaphragm, esophageal hiatus Superior esophageal sphincter • Contracted ring of circular skeletal muscle at superior end • Area where esophagus and pharynx meet • Closed during inhalation of air Inferior esophageal sphincter • Contracted ring of circular skeletal muscle at inferior end • Not strong enough by itself to stop stomach contents from regurgitating;diaphragm muscles help Process of Swallowing: Motility: the swallowing process • Swallowing, deglutition • Moving ingested materials from oral cavity to stomach; 3 phases • Voluntary phase, occurring after ingestion • Controlled by cerebral cortex • Bolus formed as ingested materials and saliva mix • Bolus directed posteriorly toward oropharynx • Pharyngeal phase • Involuntary reflex • Tactile sensory receptors stimulated • Initiate sensory input to swallowing center in medulla oblongata • Signals relayed to effectors • Effector response of pharyngeal phase • Entry of bolus into oropharynx • Elevation of soft palate and uvula to block passageway between oropharynx and nasopharynx • Move epiglottis to cover laryngeal opening • Prevents ingested material from getting into trachea • Nerve signals sent to medulla oblongata to ensure breath not taken during swallowing Esophageal phase • Involuntary phase when bolus passes through esophagus • Bolus stimulates sequential waves of muscular contraction • Propels bolus toward stomach • Superior and inferior esophageal sphincters closed at rest • Relax when bolus swallowed • Contract again afterwards, preventing reflux of materials Gross anatomy and histology of the stomach • Located in superior left abdominal quadrant, inferior to diaphragm • Chemical and mechanical digestion continues in Stomach • Digestion of protein and fat begins in stomach • Ingested materials spending 2 to 6 hours here • Absorption limited to small, nonpolar substances • Serves as “holding bag” for controlled release of partially digest material Gastric secretions • Produced by 5 types of secretory cells • 4 produce gastric juice, fifth type secretes hormone • Surface mucous cells • Line stomach lumen and extend into gastric pits • Continuously secrete alkaline product containing mucin • Mucous layer helps to prevent ulceration of stomach lining • Protects from gastric enzymes and high acidity Histologically, the entire stomach is made up of simple tubular glands and foveolae (gastric pits) and there are essentially only 2 types of mucosa: Antral (cardia, antrum and pylorus) Oxyntic (fundus and body). Describe the phases that regulate motility and secretion in the stomach. 1) Cephalic phase: initiated by thought, smell, sight, or taste of food. Stomach is then stimulated to increase contraction and release of secretions 2) Gastric phase: Initiated by presence of food in stomach. Gastrin released targeting stomach. 3) Intestinal phase: Initiated by presence of acidic chyme in duodenum. Stomach inhibited to decrease both its force of contraction and release of secretions. Cholecystokinin decreases force of contraction in stomach. Secretin inhibits release of stomach secretions. Describe the three components of the lower gastrointestinal tract Small intestine: Three continuous regions. Receives acidic chyme from stomach that mixes with accessory secretions. Most chemical digestion occurs here. Accessory digestive organs: Bile (liver and stored in gallbladder) and pancreatic juice. Neutralizes acidic chyme Large intestine: Primarily absorbs water, electrolytes, and vitamins. Completed as semifluid mass is converted to feces and eliminated via the anus. Describe the anatomy of the small intestine. • Small bowel, long tube inferior to stomach and located medially in abdominal cavity • Ingested nutrients reside in small intestine at least 12 hours • Absorbs most nutrients and large percentage of water, electrolytes, and vitamins List the glands found in the small intestine and their secretions Between the intestinal villi are invaginations of the mucosa called intestinal glands that secrete intestinal juice. Goblet cells: mucin that lubricates and protects lning and increase from duodenum to ileum Unicellular gland cells: enteropeptidase Enteroendocrine cells: release CCK and secretin in blood. Duodenal cells: only in duodenum, produces viscous, alkaline mucus protecting it from acidic chyme Explain motility within the small intestine. Smooth muscle of small intestine mixes chyme with gland secretions Describe the accessory digestive organs associated with the small intestine and the contributions of each to digestive processes. Ducts: Biliary apparatus and pancreatic ducts. Liver: main digestive function is the production of bile. Gallbladder: Stores, concentrates, and releases bile that the liver produces. Three tunics, the mucosa folds to permit distension of wall as it fills with bile. Pancreas: Endocrine cells produce and secrete hormones such as insulin and glucagon. Exocrine cells produce pancreatic juice to assist with digestive activities. Workhorse for providing digestive enzymes into the small intestine for chemical digestion. Pancreatic juice: Digests startch, triglycerides, protein, and nucleic acids. Explain how both blood and bile flow through the liver. Blood and bile flow in opposite directions because they have opposite endpoints. Blood flows towards the central vein which will ultimately put blood into the inferior vena cava heading towards the heart. What does the liver do? ● ● ● ● ● ● ● ● ● ● ● ● ● ● produces glycogen from glucose breaks down glycogen into glucose converts non-carbohydrates to glucose oxidizes fatty acids synthesizes lipoproteins, phospholipids, and cholesterol converts carbohydrates and proteins into fats deaminates amino acids forms urea synthesizes plasma proteins converts some amino acids to other amino acids stores glycogen, vitamins A,D, B12, iron, and blood phagocytosis of old RBCs and foreign substances removes toxins from blood produces and secretes bile – the only digestive function Discuss the regulation of the accessory glands associated with the small intestine Intestinal glands • invaginations of mucosa between intestinal villi • secrete intestinal juice - Goblet cells • produce mucin forming mucous • increase in number from duodenum to ileum - Unicellular gland cells • synthesize enteropeptidase (an enzyme used to convert trypsinogen to trypsin) - Enteroendocrine cells • release hormones such as CCK and GIP - Submucosal gland • produces alkaline mucus secretion protecting duodenum from chyme Name the three major regions of the large intestine and four segments of the colon of the large intestine. Cecum- first portion of the large intestine • Vermiform appendix- intraperitoneal thin sac projecting inferiorly from posteromedial cecum. • Colon- second portion of the large intestine, forms inverted U-shaped arch 1. Ascending colon- originates at ileocecal valve 2. Transverse colon- originates from right colic fixture 3. Descending colon- along left side of abdominal cavity Relatively wide tube, shorter than small intestine • Located in abdominal and pelvic cavities • From ileocecal junction to termination at anus Functions: • Absorbs water and electrolytes from remaining digested material • Watery chyme compacted into feces • Stores feces until eliminated through defecation Gross anatomy of the large intestine (continued) • Anal canal • Last few centimeters of large intestine • Lined by stratified squamous epithelium • Passes through opening in levator ani muscles and terminates at anus • Longitudinal ridges, anal columns • Depressions between, anal sinuses • Release mucus when pressure exerted • Internal anal sphincter • Involuntary smooth muscle at base of anal canal • External anal sphincter • Voluntary skeletal muscle • Sphincters normally closed off but relax during defecation Explain the distinguishing histologic features of the large intestine Lined by simple columnar, lacks intestinal villi, numerous intestinal glands Describe the bacterial action that takes place in the large intestine • Indigenous microbiota • Normal bacterial flora in large intestine • Breakdown carbohydrates, proteins, and lipids in chyme • Produce carbon dioxide, H+, other substances • Produce B vitamins and vitamin K • Absorbed from large intestine into blood • Feces is final product • Composed of water salts, epithelial cells, bacteria, undigeste material Name the three classes of carbohydrates Simple sugars. 1. Monosaccharides (glucose, fructose, galactose) 2. Disaccharides (sucrose, maltose, lactose) 3. Polysaccharides (starch and cellulose) Explain the processing in the oral cavity that initiates carbohydrate digestion Digestion of starch begins in the oral cavity. ● ● ● Salivary amylase is made and released from the salivary glands. This amylase breaks chemical bonds between glucose and starch to break down specifically the starch molecule. The larger the meal the longer salivary amylase stays active Describe the chemical digestion of carbohydrates that occurs in the small intestine ● ● ● ● ● ● ● Pancreatic amylase is made and released by the pancreas as a component of pancreatic juice into the small intestine. This enzyme continues the digestion of starch into shorter strands of glucose, maltose. To complete the whole break down the brush border enzymes dextrinase and glucoamylase which break bonds between oligosaccharides and maltase break bonds between two glucose molecules that make up maltose. Lactase digests lactose to glucose and galactose. And sucrase digests sucrose to glucose and fructose. Glucose, galactose, and fructose monomer are absorbed into the blood and are transported through the hepatic portal vein to the liver. The liver is where fructose and galactose convert into glucose. Glucose circulating the blood will be used for energy or stored as glycogen. Cellulose is a carb used as fiber Identify the enzyme that initiates protein processing in the stomach, and explain its activation and action ● Pepsin is from the inactive precursor pepsinogen released by chief cells. ● HCl that is released from parietal cells causes the low pH in the stomach that actives pepsin and denatures proteins to help their chemical breakdown. Explain why the proteolytic enzymes of the stomach and pancreas are synthesized in inactive forms All enzymes that digest proteins from both the stomach and pancreas are released as inactive. Proteolytic enzymes would destroy the cells lining the main and accessory pancreatic duct as they pass through those ducts. Describe the chemical digestion of proteins that occurs in the small intestine. ● ● ● ● ● Because of high pH three new inactive enzymes trypsinogen, chymotrypsinogen, and procarboxypeptidase form. Once these three reach the small intestine, they are activated by enteropeptidase (which is made in the small intestine) Trypsin and chymotrypsin break peptide bonds to produce smaller strands of amino acids. Carboxypeptidase removes amino acids from the carboxyl end of a protein. Dipeptidase breaks the final bond between two amino acids so they can be absorbed. Aminopeptidase makes free amino acids from the end of peptides. Explain the role of bile salts in mechanical digestion of lipids and the role of pancreatic lipase in the chemical digestion of triglycerides. ● ● ● ● ● Emulsification (breaking ice cube into ice chips) occurs from bile salts. These are produced by the liver and stored in the gallbladder. Bile salts have a polar head and nonpolar tail. They position themselves like an inverted spike ball with the fat in the center.This is what's called a micelle. So bile salts emulsify fats so that pancreatic lipases have better access to the triglyceride and can more efficiently digest it. Cholesterol is the same but it is not digested. Discuss the process by which lipids are absorbed. ● ● ● ● ● Digested monoglycerides, cholesterol, other lipids, and fat-soluble vitamins are contained in micelles. Micelles transport these to columnar cells lining the small intestine. Lipids enter while bile salts are passed on to be reused. Once in fatty acids attach to mono to form a triglyceride again. These lipid molecules are wrapped with a protein called a chylomicron. Chylomicrons pass through lymph capillaries of the small intestine and enter the blood and deliver lipids to the liver and other tissues. Describe the digestion of nucleic acids. ● ● ● ● ● ● Happens in the small intestine. A nucleotide is composed of sugar, a phosphate group, and a nitrogenous base. Deoxyribonuclease and ribonuclease, produced by the pancreas, break the phosphodiester bond between individual nucleotides of DNA and RNA. Phosphatase breaks bonds holding phosphate to the rest of it. And nucleosidase breaks the bond between sugar and a nitrogenous base. All nucleic acid components are absorbed into the blood. Chapter 27- Nutrition & Metabolism Nutrition—study of how living