Urinary System (Final Exam)

Question 1

What are the urinary organs?

Answer 1

Kidneys
Ureters
Urinary Bladder
Urethra

Question 2

What are the functions of the urinary system?

Answer 2

Water and electrolyte homeostasis:
1. filtration of cellular wastes from blood
2. selective reabsorption of water and solutes
3. regulation of fluid balance
4. maintain electrolytes homeostasis/acid base balance
Excretion of toxic metabolite waste products and excess water
Production of hormones: Renin, Erythropoietin
Regulation of blood pressure - juxtaglomerular apparatus
Activation of Vitamin D

Question 3

What is the functional unit of the kidney? How are they the site of osmoregulatioN?

Answer 3

Nephron.
Filtration of small molecules from blood plasma to form a filtrate. Selective reabsorption of most of water and other molecules from the filtrate.

Question 4

What is located within the cortex of the kidney?

Answer 4

Renal corpuscles
Proximal Convoluted Tubules
Nephron Loops (of Henle)
Distal Convoluted Tubules
Collecting Tubules
Peritubular Capillary Plexuses

Question 5

What is located within the medulla of the kidney?

Answer 5

Nephron Loops (of Henle)
Collecting ducts, Vasa Recta
Interstitial Cells

Question 6

What are the 2 main parts of a nephron?

Answer 6

Renal Corpuscle

Renal Tubules

Question 7

What are the main parts of the renal corpuscle?

Answer 7

Glomerulus

Glomerular Capsule = BOWMAN’S CAPSULE

Question 8

List and describe the cells of the renal corpuscle.

Answer 8

Podocytes - visceral layer of glomerular capsule
Squamous cells - parietal layer of glomerular cells
Endothelial cells - form fenestrated glomerular capillaries
Mesangial cells - between fenestrated capillaries

Question 9

What is the purpose of the fenestrated capillaries in the kidney?

Answer 9

Allows small molecules in blood to pass from the glomerular capillary into the urinary space of the renal corpuscle. Formed elememts, albumin and molecules larger than albumin stay in the blood.

Question 10

Where does filtrate enter the tubular system? What happens after this?

Answer 10

Filtrate enters tubular sytem via Urinary Pole.
Some molecules are reabsorbed and returned to blood of peritubular plexus and vasa recta.
Water molecules and some water remain in the tubular system and eventually will empty into the ureter; urine is stored in the bladder pending voiding.

Question 11

Describe the 3 steps in the formation of urine.

Answer 11

1. Primary (glomerular) filtrate) - produced by ultrafiltration of blood in renal corpuscle
2. Reabsorption of substances - 98% of filtrate is reabsorbed, 85% is water
3. Tubular secretion - K+, H+, NH4+

Question 12

What helps to form the blood-urine barrier?

Answer 12

1. Endothelium of glomerular capillaries - numerous pores allow passage of all non-cellular elements of blood
2. Glomerular Basement Membrane - fused basal laminae of capillaries and podocytes serve as glomerular ultrafilter - everything smaller than albumin can go through filter freely
3. Podocytes - with interdigitating trabeculae and pedicles form slit pores between processes. Form visceral part of Bowmans capsule.

Question 13

What are mesengial cells?

Answer 13

Phagocytic cells
Contractile
Have receptors for angiotensin II, ANP
provide some structural support to capillaries

Question 14

List the glomerular filtrate pathway.

Answer 14

Urinary space of Bowman’s capsule –> PCT –> Nephron loop –> DCT –> Collecting and Papillary duct –> Calyx or renal pelvis

Question 15

Describe proximal tubules

Answer 15

Begin at urinary pole of renal corpuscle.
Tubules in first portion are named PCT, lined by single layer of cuboidal tubular epithelial cells with apical microvilli or “Brush border”
Lateral borders have interdigitations of lateral cell processes thus cell limits are indistinct
Basal surface has folded membrane (basal striations)
PCT present in CORTEX ONLY - proximal straight tubules once in MEDULLA
PCT cells are absorptive - 85% of Na+ and water from glomerular filtrate are absorbed in the PCT as well as 100% of glucose and amino acids
Selectively reabsorbs Ca2+ PO4-

Question 16

Describe the similarities/differences between proximal and distal convoluted tubules.

Answer 16

Microvilli - present in PCT only

Basal Striations - folds of plasma membrane with ATP driven Na+ pump - both in PCT and in DCT

Question 17

Describe Nephon Loops (of Henle)

Answer 17

U-shaped
Thin descending and thin ascending segment and a thick straight ascending segment
Lining varies from squamous in thin segment to simple cuboidal in thick
Parallel the course of the vasa recta, facilitating ion and water exchange

Question 18

Describe Distal Convoluted Tubules

Answer 18

Begin at vascular pole of renal corpuscles
Does not have brush border (no microvili)
Has basal striations and absorptive celles
Cells of DCT are main target of Aldosterone
DCT contain specialized cells of MACULA DENSA

Question 19

What is macula densa?

Answer 19

Specialized cells of DCT adjacent to specialized smooth muscle cells (juxtaglomerular cells) of the afferent and efferent arterioles

Question 20

What are the 2 components of the Juxtaglomerular Apparatus and describe them.

Answer 20

1. Macula Densa - cells (part of DCT wall) are chemoreceptors that sense Na+ concentrations in filtrate
2. Modified smooth muscle cells - juxtaglomerular cells of mainly afferent and to a lesser degree efferent arterioles - detect variation in blood pressure (baroreceptors) and secrete renin into vessel lumen

Question 21

What are collecting ducts?

Answer 21

Collecting tubules connect to collecting ducts lined by low columnar to cuboidal cells - light (principal) and darK (intercalated) cells
Lumen contains urine of variable concentration
Terminal portion are papillary ducts which empty at the area cribrosa of the renal arest or papilla (species dependnet)

Question 22

What are the jobs of the principal and intercalated cells of the collecting ducts?

Answer 22

Principal (light) cells - reabsorb Na and H2O under ADH control
Intercalated (dark) cells - participate in acid-base balance

Question 23

What are Renal Papilla with Papillary Ducts?

Answer 23

Terminal portion of collecting ducts are papillary ducts which empty at eh Area Cribrosa of the renal arest or papilla
Vasa Recta take away water passing through collecting and papillary ducts

Question 24

What type of epithelium lines the ureter, urinary bladder and urethra?

Answer 24

Transitional Epithelium = Urothelium

Question 25

Describe the male urethra.

Answer 25

Pelvic and Penile segments.
Last part lined by stratified squamous (rest transitional)
Deferent ducts and accessory sex glands all empty products into urethrs
Vascular Stratum - corpus spongiosum

Question 26

What does the urinary tract develop from?

Answer 26

Intermediate mesoderm and the urogenital sinus.

Question 27

Describe the different between epithelium and mesenchyme?

Answer 27

Epithelium is continuous sheet of polarized cells whose apical and basal regions are separated by tight junctions. In contrast, mesenchyme comprises loosely associated nonpolarized cells.

Question 28

Describe the 3 stages of renal development in mammals.

Answer 28

Pronephros forms and regresses and then Mesonephros form.
Majority of mesonephros disappears but he mesonephric duct is retained in male and becomes the epididymis and ductus deferens.
Then the Metanephros forms - definitive kidney

Question 29

Describe in detail the pronephros stage of renal developmen

Answer 29

First structural evidence of nephrogenesis is the formation of 2 parallel epithelial tubes known as Pronephric Ducts within the intermediate mesoderm in the cranial end between the lateral and somatic mesoderm.

Question 30

Describe the mesonephros stage of renal development.

Answer 30

Pronephric ducts elongate caudally and the adjacent inermediate mesoderm transforms into epithelial tubules called mesonephric tubules.
Each mesonephric tubules receives a blood supply from a branch of the aorta, ending in a capillary tuft.
Concurrent with the intermediate mesoderm transforming into mesonephric tubules and the formation of capillary tufts allowing for filtration of blood.
The filtrate flows through the mesonephric tubule and is drained into the continuations of the pronephric duct called the Mesonephric Duct (Wolffian Duct).
The pronephros and mesonephros degenerate while the mesonephric duct extends towards the most caudal end of the embyro, ultimately attaching to the cloaca of amphibians and reptiles.

Question 31

Describe the metanephros stage of renal development.

Answer 31

The mesonephric duct develops an outpouching called the Ureteric Bud/Metanephric Duct
The elongated stalk of this later forms the ureter.
As the cranial end of the ureteric bud extends into the intermediate mesoderm, it branches to form the collecting duct system for the kidney, the major and minor calyces and the renal pelvis.