Final: Lecture 21

Question 0

Nephron

Answer 0

• Functional unit of the Kidney, approx 1 million
• Each nephron consists of: renal corpuscle composed of Bowman’s capsule and glomerulus, and renal tubule that is continuation of Bowman’s
• Empty into collecting ducts, which then empty into renal pelvis

Question 1

Sagittal section of the kidney reveals the following areas:

Answer 1

• Outer capsule surrounding the entire kidney except the hilum
• Outer cortical area beneath capsule which has cuplike form with open side of cup facing hilum
• Juxtamedullary cortex deeper
• Medullary area made up of triangular-shaped renal pyramids and divided into outer deep to jux, inner deep to outer
• Renal pelvis into which empty the renal pyramids

Question 2

Cortical Nephrons

Answer 2

• Located in the cortex
• Their glomeruli empty into peritubular capillary networks that surround proximal and distal convoluted tubules
• Have short loops of Henle that don’t extend deeply into medulla

Question 3

Juxtamedullary nephrons

Answer 3

• Renal corpuscles of these located in the cortex next to cortical-medullary junction
• Glomeruli empty into vasa recta consisting of long, straight arterioles and venuels that run parallel to the loops of Henle and collecting ducts
• Long loops of Henle that extend deeply into medulla

Question 4

Vascular supply to the Kidney

Answer 4

•Branches of the renal artery within kidney organized into the following sequene:

• Interlobar arteries
• Arcuate arteries
• Interlobular arteries
• Afferent arterioles–>Glomeruli–>Efferent arterioles
• Vasa recta or peritubular capillaries
• Interlobular veins
• Arcuate veins
• Interlobar veins
• Renal vein

Question 5

Glomerulus

Answer 5

• Afferent arteriole: juxtaglomerular cells (circular smooth muscle at vascular pole, secrete renin (hypertensive factor))
• Glomerular formation of capillaries
• Efferent arteriole

Question 6

Bowman’s capsule

Answer 6

• Double-layered, cup-shaped dilation of nephron, consists of inner and outer layer
• Parietal layer: outer layer of simple squamous epithelium, continuous with simple cuboidal epithelium of the proximal convoluted tubule
• Visceral layers: inner layer of podocytes in contact with endothelium of glomerular capillaries
• Bowman’s located between parietal and visceral layers and is continuous with the lumen of proximal convoluted tubule

Question 7

Renal Corpuscle

Answer 7

• Involved in producing a filtrate of blood
• Rest of the nephron, including convoluted portions of LOH, as well as collecting ducts involved in Modifying the filtrate
• Formation of urine involves: Filtration (in renal corpuscle), Reabsorption (in renal tubules), and Secretion (in renal tubule)

Question 8

Mesangium

Answer 8

• Part of the glomerulus
• Formed by mesangial cells embedded in a mesangial matrix
• Intraglomerular mesangial cells located between nearby capillaries in the glomerulus and cover endothelium not covered by Podocytes
• Extraglomerular located between the afferent and efferent arterioles at the vascular pole and ass. with juxtaglomerular apparatus.

Question 9

Characteristics of Mesangium cells

Answer 9

• Contractile: utilize cytoskeletal contractile proteins to modify blood flow through glomerular capillaries
• Phagocytic: take up worn out glomerular basal lamina for recycling and phagocytose immunoglobulins trapped in basal lamina
• Proliferative, synthesize matrix and collagen
• Secrete prostaglandins and endothelins*
• Respond to angiotensin II*
• Provide mechanical support and regulate blood flow

Question 10

An increase in sympathetic activity _______ renin secretion.

Answer 10

•Stimulates

Question 11

Juxtaglomerular apparatus

Answer 11

•Components of: macula densa, extraglomerular mesangial cells, and juxtaglomerular cells

Question 12

Macula densa

Answer 12

• Formed by elongated, densely packed cells in the wall of Proximal convoluted tubule. Polarity of these cells is reversed.
• Responds to changes in Na and Cl in urine or hypotensin
• Signals renin release from jux cells**
• Involved in regulation of fluid-electrolyte balance and blood pressure regulation**

Question 13

Juxtaglomerular Cells

Answer 13

• Modified smooth muscle cells ass. with macula densa and afferent arteriole
• Secrete renin into the blood when stimulated by the macula densa
• Innervated by sympathetic nerve endings with increase renin release

Question 14

Uriniferous (Renal) Tubule

Answer 14

• Simple squamous epithelium of Bowman’s Capsule becomes contiunous with simple cuboidal of proximal
• Parts of the renal tubule: proximal, descending limb of Henle (think and thin portions), LOH, Ascending limb of Henle (think and thin), distal convoluted tubule (continuous with collecting ducts)

Question 15

Proximal Convoluted Tubule characteristics

Answer 15

• Extends from the urinary pole of renal corpuscle to beginning of LOH
• Simple cuboidal made up of truncated pyramidal cells
• Apical (facing the lumen) tight junctions and brush border
• Basolateral infoldings and interdigitations
• Basal striations with abundant mitochondria
• Large, pale-staining nuclei, Eosinophilic cyto

Question 16

Loop of Henle

Answer 16

• Extends from proximal to distal convoluted tubules
• Descending and ascending limbs
• Think segments of LOH are composed of simple low cuboidal, no brush border and more basal vertical striations
• Thin segments are simple squamous epithelium, impermeable to water

Question 17

Distal Convoluted Tubule

Answer 17

• Simple cuboidal epithelium with smaller cells than those of proximal
• Larger lumen than proximal, no brush border
• Cytoplasm less eosinophilic
• Impermeable to water except in presence of ADH (antidiuretic hormone, (AKA: vasopressin) derived from posterior pituitary, functions to reduce water loss)

Question 18

Collecting Duct

Answer 18

• Different embryological origin than that of nephron
• Walls consists of simple cuboidal epithelium
• Two major specialized cells:
• Principal cells: reabsorb Na ions and water and secrete K+ via ATPase pump
• Intercalated cells: secrete either H+ ion or bicarbonate ion

Question 19

Excretory Passages

Answer 19

• Renal pelvis, ureter, and urinary bladder
• Mucosa: Transitional epithelium (urothelium) basement membrane, lamina propria of FECT, some loose lymphoid tissue and a few smooth muscles
• Muscularis: Inner longitudinal and outer circular smooth muscle coat ureter, lower thirst of ureter has third external longitudinal coat, layers of smooth muscle in urinary bladder from detrusor muscle.
• Adventitia (FECT external to muscularis, serosa over superior surface of bladder)

Question 20

Prostatic urethra (males)

Answer 20

• Section of urethra passing through prostrate gland
• Mucosa lined with transitional epithelium
• Highly vascularized with veins with abundant elastic tissue

Question 21

Membranous urethra (males)

Answer 21

• Tall pseudostratified columnar cells but variable

* Extends through urogenital diaphragm and receives striated muscle cells forming the external sphincter of bladder

Question 22

Cavenous urethra (males)

Answer 22

•Lined with pseuduostratified epithelium with patches of stratified squamous

Question 23

Glands of Male urethra

Answer 23

• Lucanae of Morgagni are invaginations of mucous membrane containing single or group of intraepithelial mucous cells
• Glands of Littre are branched tubulara glands opening into the lacunae of Morgagni

Question 24

Female Urethra

Answer 24

• Mucosa line with stratified or pseudostratified columnar epithelium with intraepithelial nests of mucous glands
• Lamina propria is highly vascularized with veins with an abundance of elastic tissue
• Submucosa is not discernible
• Muscularis has an inner longitudinal and an outer circular layer of smooth muscle cells but not well defined
• Adventitia not discernible

Question 25

Renal filtration barrie

Answer 25

• Function: separates blood in glomerular capillaries from filtrate in Bowman’s space
• Components: fenestrated endothelium of capillaries,
• basal lamina contains type IV collagen, fibronectin, laminin, heparin sulfate
• Filtration slits created by pedicles of podocytes: covered by filtration slit diaphragm, pedicels are attached to basal lamina via ab integrins

Question 26

Angiotensin II

Answer 26

• Stimulates secretion of aldosterone from adrenal cortex
• Aldosterone acts on the principal cells of the collecting ducts and the thick ascending limbs of Henle
• Increases reabsorption of Na and water which increases blood pressure
• Stimulates release of ADH

Question 27

Renin-Angiotensin-Aldosterone system:

Answer 27

•Angiogtensinogen (circulating blood protein from liver)–(Renin)–>Angiotensin I (primarily produced in lungs)–(ACE angiotensin-converting factor from pulmonary and renal endothelium)–>Angiotensin II