University:
Texas A&M University
Course:
BIOL 319 | Integrated Human Anatomy and Physiology I
Academic year:

2023
Views:

381

Pages:

124
Author:

Nicole Wang

The Urinary System Objectives Function Evolution (Smith, role of the jaw) Anatomy Kidney structure Composition of nephrons Identification of nephron components Excretory components One objective is to be able to identify these cells Nephron is the structural and functional unit of the kidney. Function of Urinary System: Homeostasis Rid body of waste (urea, uric acid, creatinine, salts) Preserves constancy of extracellular fluid in composition, volume, and pH Endocrine function a) Secrete erythropoietin - red blood cell production (endothelium of the peritubular capillaries) b) Produces renin (aldosterone release) and Medullipin I Role of the jaw Fresh water Land Salt water PORTAL ARTERIOLE Arterial Portal System Capillary Portal Arteriole Capillary = Function of portal system? 1st afferent arteriole efferent ARTERIOLE, and PERITUBULAR CAPILLARIES 2nd 1st 2nd Local change in blood composition where first capillary modifies blood and second allows the change in composition to affect local cells near it. hilum Hilus region where blood vessels enter and leave and the ureter begins hilum Cortex and Medulla of the kidney Minor calyces 458 Cortex 260 Cortex Medulla 34400 Medulla Medulla Cortex Renal capsule 19713 19713 Cortex Medulla 19713 Kidney (H&E) Apex of renal pyramid Renal calyx CT adventia capsule Renal pyramind and calyx Medulla Cortex Simple columnar to transitional-like epithelium of pyramid Renal pelvis Cortex Medulla Cortex 19713 Kidney (H&E) Arcuate arteries Segmental vein Copyright McGraw-Hill Companies Blood flow: Renal artery > segmental artery > interlobar artery > arcuate artery > interlobular artery > afferent arteriole > glomerulus > efferent arteriole > peritubular capillaries (assoc. with convoluted tubules) OR vasa recta (assoc. with loop of henle) > interlobular vein > arcuate vein > interlobar vein > segmental vein > renal vein. Interlobular artery Cortex Medulla 258 Cortex Medulla 258 kidney thin loop of Henle in cortex Thin loop of Henle in cortex Kidney (H&E) Cortex Capsule Cortex Medulla Medulla Arcuate arteries Juxtamedullary nephrons Medullary rays Portal Nephrons are the structural and functional units of the kidney. Nephrons consists of: • A glomerulus, • Bowman's capsule, • proximal convoluted tubule, • loop of Henle, • distal convoluted tubule, and • collecting tubule (collecting ducts). Efferent Arteriole, Afferent Arteriole, and Peritubular Capillaries Interstitial cells in the peritubular capillary bed secrete erythropoietin - red blood cell production Kidney Function Based on Combination of: • • • • Filtration Active Secretion Passive Diffusion Selective Absorption 258 34400 Nephrons are the structural and functional units of the kidney. Cortex 19713 Medulla Cells of the Glomerulus and Capsule Parietal epithelium Podocyte Mesangial cell Endothelial cell Parietal Epithelium Podocyte Mesangial Cell Endothelial Cell Kidney (H&E) Urinary pole Bowman's space Parietal epithelium Bowman’s capsule Podocyte Glomerulus Visceral epithelium Arteriole of vascular pole Juxtaglomerular cells Macula densa Renal corpuscle Renal corpuscle 19713 Visceral epithelium Bowman's space Glomerular endothelium Glomerular basal lamina The renal corpuscle provides the anatomical Arterioles structure required for the first phase of urine formation: the production of the Distal tubule glomerular filtrate. and macula densa Several histological Distal tubule arrangements and and macula densa structures are required for the production of glomerular filtrate: 1) arterioles entering and leaving the glomerulus, 2) glomerular endothelium, 3) glomerular basal lamina, and 258 4) visceral epithelium of the Bowman's capsule Components of the filtration barrier: 1. The fenestrations of the capillary endothelium, which blocks blood cells and platelets 2. The thick, combined basal laminae, or GBM, which restricts large proteins and some organic anions 3. The filtration slit diaphragms between pedicels, which restrict some small proteins and organic anions EM 18a The glomerular basal lamina, thick and anionic, filters macromolecule s according to their size and electrostatic charge. Glomerular Features for Extreme Filtration 19713 Very Large Surface Area (1.5 m2) Large resistance afforded by reduced diameter of the efferent arteriole Glomerular Thin Filter (0.1 µm) basal lamina Thus, 25 times more permeable The hydrostatic pressure within the glomerular capillaries provides the than regular capillaries driving force for producing 180 Endothelium of the glomerular capillaries is fenestrated liters of glomerular filtrate per day. The filtrate resembles blood plasma without large (>40,000 MW) proteins. Filtrate Blood ? Blood Filtrate Filtrate Blood Glomerulus - Passive Ultrafiltration Endothelial cell >600,000 MW Basal lamina >160,000 MW Filtration slits >40,000 MW Vascular pole 258 Urinary pole Parietal cells Glomerulus Proximal convoluted tubule EM 18b 19713 Proximal Convoluted Tubules 34400 Brush border Distal tubules Acidophilic cytoplasm Nuclei far apart Histo32 Indistinct lateral cell boundaries 19713 Human kidney cortex Proximal convoluted tubules Adventia capsule with no mesothelium The intense eosinophilia of the cytoplasm of cells in the proximal convoluted tubules results from the glycocalyx covering the brush border staining intensely eosinophilic and the high density of membranes within the cells. These membranes and the high density of PCTs in the cortex are responsible for the PCTs absorbing most of filtered water from the renal corpuscle. Renal corpuscle Kidney (PAS/Hematoxylin) Basement membranes are PAS positive Distal tubule Brush border of proximal tubule stain PAS positive due to the rich the glycocalyx covering its numerous microvilli. Brush border is involved in reabsorption of protein. Proximal convoluted tubules 19713 0 to 8 mg/dL protein in urine is considered normal. 258 Brush border Distal Convoluted Tubules No brush border Less acidophilic cytoplasm Nuclei relatively close Larger lumen Toulidine blue kidney Ascending loop of Henle Peritubular capillaries of the vasa recta Distal tubules Transition from ascending loop of Henle to distal tubules 36748 Descending loop of Henle Transition from proximal tubules to thin descending loop of Henle Rich blood supply of peritubular capillaries and vasa recta cortex 260 Arcuate arteries medulla 36748 Ascending loop of Henle Distal tubule Blood capillaries of the vasa recta Descending loop of Henle Countercurrent exchanger Capillaries of the vasa recta Peritubular Capillaries Absorbs - 180 liters/day from interstitial spaces; thus, ~4 times reabsorption of venous end of all other capillaries of body Endothelial cells - extremely porous Colloidal osmotic pressure of plasma proteins Low capillary pressure Proximity to uriniferous tubules Peritubular Capillaries Kidney medulla CT CT TnLH CT ThLH CT Cap CT Cap 19713 kidney Collecting duct Kidney (H&E) Apex of renal pyramid Renal calyx CT adventia capsule Renal pyramind and calyx Medulla Cortex Simple columnar to transitional-like epithelium of pyramid Renal pelvis kidney cortex medulla Minor calyx Transitions from ascending loop of Henle to distal tubules Enfolding of the basal cell membrane line up mitochondria in cells of the distal tubule. 36748 Juxtaglomerular apparatus Juxtaglomerular apparatus 258 Renin granules in JG cells of Kidney (PAS) Angiotensinogen (Plasma Globulin) Renin (Enzyme from JG Cells) Angiotensin I (Plasma Enzyme) Angiotensin II (Most Potent Vasoconstrictor) Increased Blood Pressure Angiotensin II Vasoconstriction Aldosterone release from Adrenals Increased Blood Pressure Increased Sodium (Water Reabsorption by Distal Tubule) Increased Blood Volume Adrenal Function Aldosterone stimulates Na+ resorption in: • Distal tubule of kidney • Gastric mucosa • Salivary glands • Sweat glands Medullary interstitial cells Produces Medullipin I which is converted to medullipin II in the liver Medullipin II in a potent vasodilator and is influenced by renal artery perfusion pressure Dural control of blood pressure by kidney Medullipin I is antihypertensive while Renin is prohypertensive peritubular fenestrated endothelium A countercurrent multiplier system is a mechanism that expends energy to create a concentration gradient. The countercurrent exchanger, a mechanism where gradients are maintained, but not established. https://www.khanacademy.org/science/health-andmedicine/human-anatomy-and-physiology/Introduction-tothe-kidneys/v/countercurrent-multiplication-in-the-kidney Cortical nephrons Loop increases temperature over straight tube with same amount of heat Juxtamedullay nephrons 19713 kidney thin loop of Henle in cortex Thin loop of Henle in cortex Arterial Portal System Capillary Portal Arteriole Capillary = Afferent arteriole, Efferent Arteriole, and Peritubular Capillaries Parathyroid Glands Parathyroid hormone (PTH) acts on Bones (osteocytes / osteoclasts), kidneys (increase reabsorption of distal tubules), and intestines (increase calcium absorption) to maintain tight control of calcium concentrations in the extracellular fluid ( 8.5 – 10.5 mg/100 mL) Calcium necessary for muscle contractions, glandular secretions, blood coagulation, and key enzymes of intermediary metabolism Removal of gland results in violent spasm of skeletal muscle (tetany) and ultimately death Flow rate Minor and major calyces are lined with transitional epithelium Ureter (upper 1/3) 1 2 3 4 1. Transitional epithelium 2. Lamina propria 3. Longitudinal smooth muscle 4. Circular smooth muscle 5. Adventia 5 Transitional epithelium Ureter – transitional epithelium and smooth muscle Ureters have three coats: 1) a mucous membrane consisting of transitional epithelium (4-5 cells thick) in longitudinal folds supported by a lamina propria of dense connective tissue, 2) a muscle coat with inner longitudinal and outer circular muscle fibers (an outermost layer of longitudinal fibers may also be present), and 3) an adventitial layer of fibroelastic connective tissue Epithelia of the Urinary System Simple Squamous Simple Cuboidal Simple Columnar Parietal, Thin Segment Proximal, Distal Tubule Proximal Tubule, Collection Ducts Pseudostratified Columnar Stratified Squamous Stratified Columnar Urethra Urethra Urethra Transitional Kidney, Ureters, Bladder, Urethra Urinary bladder 6 5 4 3 Transitional epithelium 6. Serosa 2 1 5. Outer longitudinal smooth muscle 4. Middle circular smooth muscle 3. Inner longitudinal smooth muscle 2. Lamina propria 1. Transitional epithelium Urinary bladder, monkey Adventitial layer Muscle coat Lamina propria Transitional epithelium Membranes Urinary bladder Nerve and mesothelium Transitional epithelium Smooth muscle 160 In summary Questions on the urinary system Which of the following process - structure combination(s) of the urinary tract match? a. filtration - renal corpuscle b. reabsorption of proteins - proximal tubule c. reabsorption of sugar - distal tubule d. a and b e. a, b, and c Renal corpuscles a. facilitate the interaction between the blood and uriniferous tubules b. contain parietal cells that filters the blood c. contain mesangial cells that has renin granules d. a and b e. a, b, and c Which characteristics facilitate maximal filtration of the glomerulus? a. large filter b. thin filter c. high blood pressure created by difference in the caliber of the afferent and efferent arterioles d. a and b e. a, b, and c Cortical nephrons Juxtamedullay nephrons

The Urinary System

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