Structure and Function of Kidney

Question 1

Cortex

Answer 1

Most superficial region, produces erythropoietin, receives most of the blood flow and is mostly concerned with reabsorbing filtered material, contains about 1 million nephrons

Question 2

Medulla

Answer 2

Deep to cortex, highly metabolically active area, which serves to concentrate urine, NO arteries penetrate the medulla, Wedge-shaped tissue masses call renal pyramids (8-12 in a kidney)

Question 3

Pyramids

Answer 3

Made up of loops of Henle and collecting tubules, renal columns separate pyramids, each pyramid and its surrounding tissue constitutes one of approximately 8 lobes of a kidney

Question 4

Minor/major calyces

Answer 4

Each major calyces subdivides to form several minor calyces (cup shaped areas that enclose the papilla.
Calyces collect urine, which drains continuously from the papillae and empty it into the renal pelvis

Question 5

Renal pelvis

Answer 5

Funnel-shaped tube, continuous with the ureter leaving the hilum, collects urine for excretion, branching extensions of the pelvis form 2-3 major calyces

Question 6

Renal interstitium

Answer 6

Peritubule and periarterial space, located between the nephrons, ureteric epithelia and renal vasculature, composed of renal support cells, including fibroblasts and macrophages and interstitial cells

Question 7

Afferent/efferent arterioles

Answer 7

Afferent: Arises from the cortical radial arteries to supply the glomerulus
Efferent: Leave the glomerulus to form the peritubular capillaries

Question 8

Bowman’s capsule

Answer 8

Part of the renal corpuscle. It consists of a visceral layer of podocytes closely applied to the glomerulus and an outer parietal layer

Question 9

Glomerulus

Answer 9

One of the capillary networks that are part of the renal corpuscles in the nephrons of the kidney. Each is surrounded by a Bowman’s capsule, the site of renal filtration, which is the first step in the formation of urine

Question 10

Juxtaglomerular apparatus (JGA)

Answer 10

initiates the renin-angiotensin mechanism to elevate blood pressure and increase sodium retention. Juxtaglomerular cells of the afferent arteriole and the macula densa of the distal tubule

Question 11

Convoluted tubule

Answer 11

Proximal tubule
Distal tubule 
Ascending Loop of Henle
Descending Loop of Henle
Collecting duct

Question 12

Major excretory functions of the kidney

Answer 12

Excretion of waste products (urea, uric acid, creatinine, breakdown products of hemoglobin, etc.), excretion of hormones, drugs and their byproducts, play a role in clearance: a concept that leads to a way to measure and assess kidney function (insulin clearance and creatinine clearance)

Question 13

Glomerular filtration

Answer 13

First step in urine formation, glomerular capillaries are relatively impermeable to proteins and devoid of cellular elements (like RBCs).
Small charged molecule (Na, K, wastes, small hormones, H2O) are able to pass through

Question 14

Tubular reabsorption and secretion

Answer 14

A very small percentage of the glomerular filtrate actually leaves the body. Most of the volume of the filtrate is reabsorbed in the proximal convoluted tubule and back out to the blood capillaries. Reabsorption does take place in the loop of Henle and the distal convoluted tubule as well. Most of the filtrate reabsorbed includes H2O, sodium ions, and most of the glucose. Secretion is the process which involves substances being added to the tubular filtrate, which will eventually be removed from the body and maintain a healthy pH. The substances secreted into the tubular fluid include potassium, hydrogen ions, ammonium ions, creatinine, urea.

Question 15

Assessment of glomerular filtration rate/ clinical relevance

Answer 15

Glomeurlar filtration rate describes the flow rate in which filtered fluid runs through the kidney. In the average adult human the GFR is about 125 ml/min or 180 L/day. The glomerular filtration rate gauges how well your kidneys are functioning and removing excess wastes and fluids. The GFR is calculated through a mathmatical formula that looks at several different factors including age, weight, sex, and creatinine levels.
**The clinical relevance of the GFR is that it is important in diagnosing the progression or improvement of chronic kidney disease. It is also a useful tool in dosing certain medications that are easily excreted by the urine.

Question 16

Proximal Tubule

Answer 16

Receives the ultrafiltrate from the urinary space of the Bowman’s capsule. It reabsorbs 50-60% of solute and water filtered at the glomerulus.

Question 17

Distal Tubule

Answer 17

Starts at the macula densa, is about 5 mm long. Its epithelium is lower than that of the proximal tubule, and although a few microvilli are present, there is no distinct brush border. It is responsible for reabsorption of sodium, bicarbonate ions, and it secretes ammonia.

Question 18

Ascending Loop of Henle

Answer 18

Is impermeable to water, but permeable to sodium chloride. Filtrate becomes increasingly dilute as salt is reabsorbed.

Question 19

Descending Loop of Henle

Answer 19

Freely permeable to water, not permeable to sodium chloride. Filtrate becomes increasingly concentrated as water leaves by osmosis.

Question 20

Collecting duct

Answer 20

Water reabsorption through aquaporins regulated by ADH. Sodium reabsorption and potassium secretion regulated by aldosterone. Hydrogen and HCO3- reabsorption or secretion to maintain blood pH. Urea reabsorption increased by ADH.

Question 21

Major non-excretory functions of the kidney

Answer 21

regulate salt content of extracellular fluid, regulate salt concentration of body, regulate potassium homeostasis, acid-base balance, mineral-bone metabolism, function as endocrine gland