Histo block III: urinary system and kidneys

Question 1

the urinary system consist of:

Answer 1

1.The paired kidneys
2.The minor and major calyces of each kidney which are expansions of the ureter
3.The ureters
4.The bladder
5.The urethra

Question 2

what are the functions of the kidney as homoestasis?

Answer 2

*Excretion waste products
*Conservation water, electrolytes & metabolites
*Regulation body fluid composition & volume
*Maintain acid-base balance

Question 3

what are the functions of the kidneys as endocrine organ?

Answer 3

*Synthesis & excretion of erythropoetin (for red blood cell development)
*Synthesis & secretion of renin as part of the renin-angiotensin-aldosterone system
*Hydroxylation of 25-OH vitamin D3 to hormonally active 1,25-(OH)2-vitamin D3

Question 4

what does the medulla of the kidney consists of?

Answer 4

The medulla consists of renal pyramids with their wide base adjacent to the cortex and their tips projecting into the minor calyces

Question 5

What lies between the renal pyramids?

Answer 5

the cortex may project down as the renal columns partially separating the renal pyramids

Question 6

how many pyramids are there?

Answer 6

Each renal pyramid corresponds to a lobe of the kidney. Generally are 8 – 12 (18) lobes.

Question 7

what is th efunction of the pyramids?

Answer 7

Function in the kidney is a result of a tight coupling between a system of epithelial lined tubules and blood vessels to remove waste products from the blood in the form of urine

Question 8

what is the basic functional unit in the kidney?

Answer 8

uriniferous tubule which consists of 2 major parts the nephron and the connecting tubule and collecting duct

Question 9

what does the nephron consists of?

Answer 9

−Renal corpuscle (Bowman’s capsule plus glomerular capillaries) (1)
−Proximal convoluted tubule (2)
−Proximal straight tubule (Descending thick limb of the loop of Henle) (3)
−Descending limb of thin segment of the loop of Henle (4)
−Ascending limb of thin segment of the loop of Henle (5)
−Distal straight tubule (Ascending thick limb of the loop of Henle) (6)
−Juxtaglomerular apparatus (7)
−Distal convoluted tubule (8)

Question 10

WHat are the 3 types of nephrons and their functions?

Answer 10

1) Cortical (superficial) nephrons:
- in outer cortex (subcapsular)
- with a short loop of Henle

2) Intermediate nephrons:
- with an intermediate length loop of Henle

3) Juxtamedullary nephrons:
- near corticomedullary border
- about 1/8 of nephrons
- extend far into medulla
- long loop of Henle
- primarily responsible for concentration of urine

Question 11

by what is the cortex and th emedulla defined?

Answer 11

Cortex:
*cortical labyrinth
*medullary rays

Medulla:
*Outer medulla composed of outer and inner stripe regions
*Inner medulla

Question 12

explain the cortical labyrinth

Answer 12

the renal corpuscles (1), proximal convoluted tubule (2), distal convoluted tubule(8) and connecting tubule (9)

Question 13

explain the medullary rays

Answer 13

the cortical portions of the proximal straight (3), distal straight tubules (6), and the cortical collecting ducts (10) from the adjacent uriniferous tubules run parallel to each other in the cortex and continue into medulla

Question 14

the lobule of the kidney is centered around?

Answer 14

the medullary rays which contain the duct system draining that lobule

Question 15

the medulla of the kidney is divided into?

Answer 15

outer medulla and an inner medulla based on the segments of the uriniferous tubule presen

Question 16

the outer medullar is subdivided into?

Answer 16

outer stripe (closest to cortex) and an inner stripe (closest to inner medulla)

Within the outer stripe are segments of both the proximal straight (3) & distal straight tubules (6) & collecting ducts (11) & occasional thin segments

Within the inner stripe only the distal straight tubule (6), thin segments (4,5), & collecting ducts (11,12) are found

Question 17

explain the contents of the inner medulla of the kidney

Answer 17

only thin segments & collecting ducts (12) are present

Question 18

what is the function of the glomerular capillaries and renal corpuscle?

Answer 18

give rise to an ultrafiltrate which becomes the proto-urine.

Question 19

explain the arterial blood supply of the cortex of the kidney

Answer 19

*The segmental arteries enter at the hilus, and give rise to the interlobar arteries which pass up between the renal pyramids and arch over to give the arcuate arteries between the cortex & medulla

*Midway between medullary rays, arcuate arteries give off interlobular arteries into the cortex where they give rise to afferent glomerular arterioles (1 per glomerulus).

*Afferent glomerular arteries give rise to glomerular capillaries which give rise to efferent glomerular arterioles

*Efferent arterioles give rise to either peritubular capillaries or vasa rectae capillaries

Question 20

summarize the function of the renal corpuscle

Answer 20

Site of the renal filtration barrier which acts in initial filtration of the blood to remove toxic components that will be excreted in the urine.

Other useful molecules and ions may also pass through the filtration barrier but will then be reabsorbed by the following segments of the nephron as needed.

Question 21

summarize the proximal tubule (convoluted and straight) fucntion

Answer 21

The major site for reabsorption (recovery) of components of the ultrafiltrate (urine) needed by the body.

Approximately 65 – 80% of the water, close to 100% of the glucose, ~98% of amino acids, peptides, proteins, and a major fraction of the Na+, Cl-, and bicarbonate ions are recovered from the filtrate for use by the body

Question 22

summarize the loop of henle (thin segment and distal straight tubule)

Answer 22

Site of establishment of a hyperosmotic gradient of salts in the medulla required for the production of a hyperosmotic concentrated urine

This hyperosmotic gradient of salts in conjunction with the collecting ducts (under the influence of antidiuretic hormone) is important for reabsorption of excess water from the lumen of the collecting ducts to produce a hyperosmotic concentrated urine necessary for land dwelling animals

Question 23

summarize the juxtaglomerular apparatus function

Answer 23

The juxtaglomerular apparatus is involved in auto-regulation of the glomerular filtration rate (GFR) and regulation of blood pressure through the release of the hormone renin.

It functions as part of the renin-angiotensin-aldosterone mechanism for control of blood pressure

Question 24

summarize the distal convoluted tubule function

Answer 24

The distal convoluted tubule plays an important role in the final adjustments of Na+, Cl-, K+ and divalent Ca+2 and Mg+2 levels (electrolyte concentrations) and acid-base levels for the body

In addition, the second portion (DCT2 segment) of the distal convoluted tubule along with the collecting tubule/duct is a major target of the adrenal hormone aldosterone, and thus it along with the juxtaglomerular apparatus plays a key role in blood pressure control

Question 25

summarize the collecting tubule and collecting duct function

Answer 25

They play a key role in the reabsorption of additional water from the urine in response to antidiuretic hormone (ADH) to produce a more concentrated hypertonic urine, thus conserving water for the body.

They also contribute to maintenance of the acid-base balance through secretion of H+ or bicarbonate ion into the urine as needed

Question 26

summarize the function of the minor and major calyces

Answer 26

They collect the urine from the kidney for transfer to the ureter

Question 27

summarize the function of the ureter

Answer 27

The ureter transports the urine to the bladder for storage

Question 28

summarize the function of the bladder

Answer 28

Storage of the urine until urination (micturition)

Question 29

summarize the function of the urethra

Answer 29

Transport of the urine from the bladder to outside the body for urination (micturition)

Question 30

summarize the function of the renal corpuscle in the neprhon

Answer 30

Site of the renal filtration barrier which acts in initial filtration of the blood to remove toxic components that will be excreted in the urine.

Other useful molecules and ions may also pass through the filtration barrier but will then be reabsorbed by the following segments of the nephron as needed

Question 31

what is the renal corpuscle and where is it found

Answer 31

The renal corpuscle found within the cortical labyrinth region of the cortex is the site where an ultrafiltrate of the blood called urine is initially formed. The body produces approximately 180 liters/day of the ultra-filtrate.

Question 32

what happens to the unfiltrate?

Answer 32

The ultrafiltrate is subsequently modified by the various tubule cells in the uriniferous tubule to: (1) reabsorb most of the water, (2) to retain important molecules such as various ions, sugars, amino acids, nucleotides and (3) to secrete toxic substances into it for removal from the body.

Question 33

what are the two major components of the renal corpuscle?

Answer 33

1.Glomerulus: a series of capillary loops (capillary bed) which produces the ultrafiltrate from blood

2.Bowman’s capsule: which is a double walled cup-shaped structure surrounding the glomerular capillaries

*Bowman’s capsule and glomerulus together are referred to as a renal corpuscle.

Question 34

afferent and efferent arterioles enter and exit at the:

Answer 34

vascular pole – site where embryonically the afferent glomerular arteriole invaginated the blind ended nephron (Bowman’s capsule) to form a “knot” of capillaries, a glomerulus (capillary bed #1).

Question 35

the glomerulus is drained by:

Answer 35

an efferent glomerular arteriole (a portal vessel).

Question 36

what is the urinary pole?

Answer 36

The other end of Bowman’s capsule where it joins proximal tubule