Microanatomy Lecture 5

Question 1

List two hormones produced in the kidney and their functions

Answer 1

1. renin: converts angiotensinogen to angiotensin I (which is then converted to angiotensin II in lungs which stimulates aldosterone) - aldosterone released by adrenal cortex to stimulate distal tubule to reabsorb sodium and water (raising blood pressure)
   * *rate limiting enzyme**
2. erythropoietin: promotes erythrocyte formation in bone marrow by stimulating proliferation, differentiation, and survival of precursor cells
   * *synthesis stimulated by hypoxia**

Question 2

How would you define a renal lobule?

Answer 2

a medullary ray (medullary tissue that projects up into the cortex consisting of collecting tubules and their accompanying proximal and distal tubules) and its surrounding cortical tissue

Question 3

The projection of each medullary pyramid into the lumen of a minor calyx is called ____________________

Answer 3

renal papillae

Question 4

What components of a nephron are contained within a medullary ray?

Answer 4

collecting tubules and their accompanying proximal and distal tubules

Question 5

What is normally contained within the urinary space?

Answer 5

between visceral layer of Bowman’s capsule with podocytes and parietal layer (simple squamous)
-receives glomerular filtrate

Question 6

Which component of the nephron begins at the urinary pole of Bowman’s capsule? Type of epithelium?

Answer 6

proximal tubule (convoluted portion followed by straight portion)

Question 7

What are the three components of the kidney filtration barrier?

Answer 7

1. capillary epithelium (fenestrated, no diaphragms, blocks blood cells and platelets)
2. shared basement membrane (restricts large proteins >70kd)
3. podocytes (filtration slits between secondary processes)

Question 8

What specialization of the apical surface of the epithelium lining the proximal tubules creates the brush border?

Answer 8

simple cuboidal epithelium (specialized for reabsorption and secretion)

Question 9

In which parts of the nephron are intercellular boundaries between epithelial cells not visible with a light microscope?
Where are they clearly visible?

Answer 9

proximal tubule, loop of henle, distal tubule

clearly visible: collecting tubules and ducts (increases from cuboidal to columnar in ducts)

Question 10

List the three parts of the loop of Henle

Answer 10

descending straight portion of the loop of henle, the thin segment, and the ascending straight portion of the distal tubule
-located mostly in the medulla

Question 11

What are the distinguishing morphological characteristics of the macular densa?

Answer 11

modified epithelial sells in the wall of the distal tubule - columnar epithelium with nuclei close together
part of the distal tubule

Question 12

Which type of nephron has the longest thin segments of the loop of Henle?

Answer 12

juxtamedullary (as compared to superficial and intermediate)

Question 13

What type of epithelium is present in the thin segment of the loop of Henle?

Answer 13

simple squamous

Question 14

What is responsible for the production of renin?

Answer 14

juxtaglomerular apparatus (macula densa, juxtaglomerular cells (smooth muscle cells), and extraglomerular mesangial cells)

Macula densa monitors ionic composition and signals JG when to release renin

Question 15

What type of cilia are found in the kidney?

Answer 15

non-motile (9+0 microtubule) = sense fluid flow in uriniferous tubule and regulate cell proliferation
in polycystic kidney disease - lead to cellular over proliferation and cyst formation

Question 16

What are the components of the extrarenal collecting system?

Answer 16

minor and major calyces, renal pelvis, ureter, bladder and urethra

Question 17

What is the histologic structure of the extrarenal collecting system?

Answer 17

1. mucosa (transitional epithelium)
2. thin lamina propria of connective tissue
3. muscularis (loss anastomosing strands of smooth muscle separated by abundant connective tissue)
4. adventitia (connect tissue)

Question 18

What are the differences between the male urethra and the female urethra?

Answer 18

male: pseudostratified columnar epithelium - long, divided into 3 segments (prostatic, membranous, penile)
female: stratified squamous epithelium - thick layer of smooth muscle in wall - relatively short