Urinary System Ch 25

Question 1

The kidneys regulate the bodies internal environment by:

Answer 1

Regulating total water volume and solutes (Osmolality)
Regulating concentrations of ions in extra-cellular fluid
Ensuring long term acid-base balance.
Excreting metabolic wastes and toxins
Producing erythropoietin and renin
Converting vitamin D to it’s active form
Carrying out glyconeogenesis during fasting

Question 2

3 layers of supportive tissue that surround the kidneys

Answer 2

Renal fascia: outermost layer of fibrous connective tissue that anchors the kidneys
Perirenal fat capsule: A fatty mass that surrounds and cushions the kidneys.
Fiberous capsule: transparent capsule that protects the kidney from infection.

Question 3

3 region of the kidneys

Answer 3

Cortex: Light colored superficial surface
Medulla: deeper dark reddish cone shaped tissue masses called renal pyramids.
Pelvis: funnel shaped tube continuous with the ureter leaving the hilum. ( branching extensions form the major and minor calyces.

Question 4

Renal corpuscle

Answer 4

A tuft of capillaries called a glomerulus and a cup shaped Bowmans capsule.

Question 5

Glomerulus

Answer 5

capillaries with fenestration to allow large amounts of solute rich (protein free) fluid which becomes filtrate.

Question 6

Glomerular Capsule

Answer 6

External parietal and visceral layer that clings to the glomerular capillaries.

Question 7

Renal Tubule

Answer 7

Consists of:
Proximal Convoluted tubule
Nephron Loop
Distal Convoluted Tubule
and connects to the collecting duct

Question 8

Proximal convoluted tubule (PCT)

Answer 8

Luminal (Apical) surface is covered with microvilli to increase surface area. Consists of cuboidal epithelial cells
The most active reabsorbers

Question 9

Nephron Loop (Loop of Henle)

Answer 9

U shaped loop has descending and ascending limbs.
The proximal part of the descending limb is continuous with the PCT and its cells are similar. The descending “thin” limb consists of simple squamous epithelium. There are thick and thin segments of the ascending and descending limbs
The rule for water is that it leaves the descending limb but not the ascending limb. The opposite it true for solutes.

Question 10

Distal convoluted tubule

Answer 10

made of cuboidal cells confined to the cortex and lack microvilli.
Fine tuning for the small amount of filtrate before it becomes urine.

Question 11

Collecting duct

Answer 11

Each collecting duct receives filtrate from many nephrons. They contain two cell types:
Principal cells: more numerous and have sparse short microvilli for maintaining the bodies water Na+ balance
Intercalated cells: Cuboidal cells with abundant microvilli (types A&B) play a role in acid-base balance of the blood

Question 12

Classes of nephrons

Answer 12

Cortical: 85% of all nephrons and are located in the cortex except for a small part of their loops that dip in the medulla.
Juxtamedullary: Originate close to the cortex and play a role in the kidney’s ability to produce concentrated urine. Long nephron loops that deeply invade the medulla.

Question 13

Nephron Capillary Beds

Answer 13

Glomerulus: Produce filtrate

Peritubular and Vasa Recta: reclain that filtrate

Question 14

Glomerulus capillaries

Answer 14

capillaries run in parallel, both fed and drained by arterioles (afferent and efferent)

Question 15

Peritubular Capillaries

Answer 15

Cling close to the adjacent renal tubules
fed by the high resistant efferent arterioles so the only have low pressure so they readily reabsorb water and solutes from the tubule cells.

Question 16

Vasa Recta

Answer 16

“straight vessels” Extend deep into the medulla paralleling the longest nephron loops.

Question 17

Juxtaglomerular Complex (JGC)

Answer 17

JGC includes 3 populations of cells that help regulate the rate of filtrate formation and systemic blood pressure: macula densa, granular cells and exteragromerular mesangial cells

Question 18

Macula densa

Answer 18

Chemoreceptors that monitor NaCl content of the filtrate entering the DCT

Question 19

Granular cells

Answer 19

In the arteriolar walls

Question 20

3 processes for urine formation

Answer 20

1. Glomerular filtration
2. Tubular reabsorption
3. Tubular secretion

Question 21

Glomerular Filtration

Answer 21

Passive process in which hydrostatic pressure forces fluids and solutes through a membrane.

Question 22

Filtration membrane

Answer 22

Fenestrated endothelium: allow blood components, not blood cells, to pass through.
Basement membrane: middle layer that blocks all but the smallest proteins and solutes from passing through.
Podocytes: visceral layer that has foot processes with filtration slits that bock any macro molecules that may have sneaked through.

Question 23

Pressure that affect filtration

Answer 23

Hydrostatic pressure in glomerular capillaries the outward pressure from the BP.
The inward pressures that oppose it are:
Hydrostatic pressure in capsule itself and colloid osmotic pressure in glomerular capillaries.

Question 24

Net filtration pressure

Answer 24

The forward pressure remaining when you take the outward pressure minus the inward pressure opposing it. This largely determines the GFR

Question 25

Glomerular Filtration Rate (GFR)

Answer 25

The volume of filtration formed each minuet by the combined activities of all 2 million gomeruli in the kidneys

Question 26

Factors affecting the GFR

Answer 26

Net filtration rate: the main controllable factor, controlled by dilation and constriction of the afferent and efferent arterioles.
Total surface area available for filtration.
Filtration membrane permeability

Question 27

Intrinsic controls of renal regulation

Answer 27

Renal auto regulation: by adjusting its own resistance to blood flow the kidney can maintain almost constant GFR:
Myogenic mechanism and Tubuloglomerular feedback mechanism.

Question 28

Myogentic Mechanism

Answer 28

Vascular smooth muscle property to relax when not stretched and contract when stretched. In this was the pressure going into the gloerulus is kept constant.

Question 29

Tubular feedback mechnism

Answer 29

Directed by the macula densa cells of the JGC located in the walls of the ascending limb and respond to NaCl concentration. Release vasoconstriction chemicals in response to high NaCl and cause the afferent arterioles to constrict.

Question 30

Extrinsic controls

Answer 30

Purpose to maintain BP:

1. Sympathetic NS controls
2. Renin-angiotensin-aldosterone mechanism.

Question 31

Sympthetic NS controls

Answer 31

Serve the body as a whole, kidneys com second in the case of hypovolemic shock. The blood is shunted away from the kidneys to other more vital organs to raise BP.

Question 32

Renin-Angiotension-Aldosterone Mechanism

Answer 32

Low BP causes the granular cells to release Renin by one of three pathways:
Direct stimulation on granular cells
Stimulation of granular cells by input of activated macula densa cells.
Reduced stretch of granular cells

Question 33

Tubular Reabsorbtion

Answer 33

Selective transepithelial process that begins as soon as the filtrate enters the proximal tubules. This reclaims most of the filtrate and returns it to the blood.

Question 34

Reabsorption of sodium

Answer 34

80% of active transport energy goes to reabsorbing sodium.
1. transport across the basolateral membrane: primary active transport by ATPase Na+ K+ pump then it is swept to the adjacent pretubular capillaries because of the high osmotic pressure in the capillaries.

Question 35

Reabsorption of Nutrients water and ions

Answer 35

Na+ reabsorption provides the energy for almost every other substance.