Week 1 - Urinary System, Kidney Structure, Kidney Physiology, Urine

Question 1

organs of the urinary system and their general function(s)

Answer 1

kidneys

Kidneys regulate blood volume and composition; help regulate blood pressure, pH, and glucose levels; produce two hormones (calcitriol and erythropoietin); and excrete wastes in urine.

renal pelvis

From the major calyces, urine drains into a single large cavity called the renal pelvis

ureters

Ureters transport urine from kidneys to urinary bladder.

bladder

Urinary bladder stores urine and expels it into urethra

urethra

Urethra discharges urine from body

Question 2

shape and size of kidneys

Answer 2

10–12 cm (4–5 in.) long, 5–7 cm (2–3 in.) wide, and 3 cm (1 in.) thick—about the size of a bar of bath soap—and has a mass of 135–150 g (4.5–5 oz).

Question 3

location of kidneys

Answer 3

a) their relationship to the parietal peritoneum and vertebral column

retroperitoneal position

b) the position of the right kidney in relation to the left kidney

Contralateral to each other

Question 4

State features of the external structure of the kidney and function

Answer 4

i) renal capsule

s- dense irregular connective tissue

f- It serves as a barrier against trauma and helps maintain the shape of the kidney

ii) adipose capsule

s- mass of fatty (adipose) tissue surrounding the renal capsule

f- protects the kidney from trauma and holds it firmly in place within the abdominal cavity

iii) renal fascia

s- thin layer of dense irregular connective tissue

f- anchors the kidney to the surrounding structures and to the abdominal wall. On the anterior surface of the kidneys, the renal fascia is deep to the peritoneum.

iv) renal hilum

s- concave border indentation

f- through which the ureter emerges from the kidney along with blood vessels, lymphatic vessels, and nerves

Question 5

Recognize that the kidneys assist in the maintenance of homeostasis by

Answer 5

elimination of wastes

maintenance of fluid and electrolyte balance

maintenance of acid-base balance

regulation of arterial blood pressure

secretion of the hormone erythropoietin

Question 6

urtheras

Answer 6

a) their location in relation to the parietal peritoneum, kidney and bladder

coming out of the renal hilum, then goes to bladder at a oblique attachment in a retoperitoal place.

b) the three coats composing the walls and their respective functions.

epithelium/muscosa (transition epithelium) - lining of the cavity

lamina propria-areolar connective tissue

muscularis (smooth muscles) - help dilate or contract lumen

adventita (fibroelastic connective tissue)- helps protect and also hold into place

c) the significance of their oblique attachment to the bladder

makes it so that urine does not travel back up the ureters but stays in the bladder thanks to to a fold made by the bladder and ureters which happens because of their oblique attachment

Question 7

State one function of the ureters

Answer 7

carry urine from the kidneys to the bladder

Question 8

Describe the urinary bladder

Answer 8

a) its location in relation to the symphysis pubis

sits between the pelvic bone, the symphysis pubis is superficial to the bladder

b) the type, location and function of the three coats that make up the wall of the urinary bladder

musocsa (transiitonal epithelium) mucosa, a mucous membrane composed of transitional epithelium and an underlying lamina propria similar to that of the ureters. The transitional epithelium permits stretching. Rugae (the folds in the mucosa) are also present to permit expansion of the urinary bladder.

lamina propia (connective tissue)

muscularis (smooth muscle tissue) - smooth muscle fibers: the inner longitudinal, middle circular, and outer longitudinal layers helps contract bladder

adventita (aeolar connective tissue) - protects and holds in place

c) the three openings of the bladder

two openings for the ureters and one to the urethra

d) a definition of “trigone”

a smooth triangular region of the internal urinary bladder formed by the two ureteric orifices and the internal urethral orifice

Question 9

State two functions of the urinary bladder

Answer 9

hold and also excrete urine

Question 10

urethra

Answer 10

a) the type of membrane lining the urethra

inner mucosa that consists of transitional, stratified columnar, and stratified squamous epithelium; thin middle layer of circular smooth muscle; thin connective tissue exterior.

b) the location relative to the pelvic floor

through the pelvic floor

c) muscle tissue and type of control of the internal and external sphincters

external (skeletal muscle)-voluntarily controls opening and closing of urethra

internal (circular smooth muscle)-involuntarily controls opening and closing of urethra

d) the location and function of the urinary meatus (external urethral orifice)

opening of urethra to out of body, expells waste.

Question 11

male vs female urethra

Answer 11

a) the anatomical location and length

female is shorter and more deep into the body than the males which is longer

b) the specific function(s) of each

both are used to excrete urine out of. But the males urethra also excretes semen when aroused

Question 12

two parts of a nephron

Answer 12

renal corpuscle

f- which is designed to filter the blood

renal tubule

f- which is designed to modify the contents of the filtrate after it leaves the Bowman’s capsule

renal tubule into which the filtered fluid (glomerular filtrate) passes

Question 13

two parts of the renal corpuscle

Answer 13

a) glomerulus

capillary network

b) Bowman’s capsule (glomerular capsule)

a double-walled epithelial cup that surrounds the glomerular capillaries.

Blood plasma is filtered in the glomerular capsule, and then the filtered fluid passes into the renal tubule

Question 14

Outline the path the filtrate follows from the Bowman’s capsule cavity until it leaves the papillary ducts.

Answer 14

FLOW OF FLUID THROUGH A CORTICAL NEPHRON

Glomerular (Bowman’s) capsule

Proximal convoluted tubule

Descending limb of the nephron loop

Ascending limb of the nephron loop

Distal convoluted tubule (drains into collecting duct)

Question 15

Outline the pathway that blood flows through from its point of entry into the kidney to its point of exit, considering the:

Answer 15

1. renal arterty
2. segmental artrerty
3. Interlobar arteries
4. Arcuate arteries
5. Cortical radiate arteries
6. Afferent arterioles
7. Glomerular capillaries
8. Efferent arterioles
9. Peritubular capillaries
10. Peritubular venules
11. Cortical radiate veins
12. Arcuate veins
13. Interlobar veins
14. segmental vein
15. Renal vein

Question 16

unique features of kidneys vascular system

Answer 16

a) the names and type of vessel entering and exiting the glomerulus

entering is the afferent arteriole and leaves by an efferent arteriole

b) the functional significance of these vessels

Afferent arteriole carries blood to the glomerulus. Efferent arteriole takes blood away from the glomerulus.

c) the specific location of the two capillary beds which the blood flows through

glomerular bed

Question 17

renal tubule make up

Answer 17

a) type of tissue which makes up the wall of the renal tubule

simple squamous epithelium

b) similarities and difference in cell structure between the proximal convoluted tubule and the distal convoluted tubule

Distal convoluted tubule (DCT) by simple cuboidal epithelium and the proximal convoluted tubule (PCT) by brush bordered simple cuboidal epithelium to increase the area for absorption

Question 18

juxtaglomerular apparatus

Answer 18

a) location and overall purpose as part of the nephron structure

the structure that actually produces urine in the process of removing waste and excess substances from the blood. located in the kidneys in the medulla cortex

b) define/describe macula densa

a collection of specialized epithelial cells in the distal convoluted tubule that detect sodium concentration of the fluid in the tubule

c) define/describe juxtaglomerular cells

derived from smooth muscle cells, of the afferent arteriole secrete renin when blood pressure in the arteriole falls

d) name the enzyme secreted by the juxtaglomerular cells

renin

Question 19

renin

Answer 19

a) the stimulus for its release

which sense changes in renal perfusion pressure, via stretch receptors in the vascular walls. blood pressure falls and it is released

b) the action of this ENZYME

increases blood pressure. the kidneys release the enzyme renin into the bloodstream. Renin splits angiotensinogen, a large protein secreted from the liver that circulates in the bloodstream into pieces

c) ultimate effect on blood pressure once renin has been released

increases blood pressure and regulates volume

Question 20

three processes that form urine

Answer 20

a) glomerular filtration

The principle of filtration—the use of pressure to force fluids and solutes through a membrane

Fenestration (pore) of glomerular endothelial cell: prevents filtration of blood cells but allows all components of blood plasma to pass through

Basement membrane of glomerulus: prevents filtration of larger proteins

Slit membrane between pedicels: prevents filtration of medium-sized proteins (Podocyte of visceral layer of glomerular (Bowman’s) capsule)

b) tubular reabsorption

the process that moves solutes and water out of the filtrate and back into your bloodstream.

c) tubular secretion

the transfer of materials from peritubular capillaries to the renal tubular lumen

Question 21

State for each of the following processes:

i) glomerular filtration
ii) tubular reabsorption i
ii) tubular secretion
a) areas of nephron in which it occurs
b) examples of substances moved
c) whether process occurs due to active or passive movements

Answer 21

i) glomerular filtration

a) areas of nephron in which it occurs

The Bowman’s capsule

b) examples of substances moved

filter excess fluid and waste products out of the blood into the urine collecting tubules of the kidney

c) whether process occurs due to active or passive movements

passive

ii) tubular reabsorption

a) areas of nephron in which it occurs

proximal part of the tubule

b) examples of substances moved

Ca++, Na+, glucose, and amino acids must be reabsorbed by the nephron to maintain homeostatic plasma concentrations

c) whether process occurs due to active or passive movements

both

iii) tubular secretion

a) areas of nephron in which it occurs

rom the proximal convoluted tubule to the collecting duct at the end of the nephron

b) examples of substances moved

such as urea, K+, ammonia (NH3), creatinine, and some drugs are secreted into the filtrate as waste products.

c) whether process occurs due to active or passive movements

both

Question 22

renal capsule

Answer 22

a) structure of visceral and parietal layers of Bowman’s capsule

The parietal layer comprises Bowman’s capsule and the cells are squamous, whereas the visceral layer is composed of the podocytes that have a more cuboidal shape and play a role in filtration of blood.

b) the structural difference of the endothelium of the glomerulus and capillaries of other tissues

A unique feature of glomerular endothelial cells is their fenestrations—holes in the cell that permit passage of fluid across the glomerular capillary wall

c) the diameter of afferent and efferent arterioles

afferent are way bigger than efferent arterioles

Question 23

why are the afferent and efferent arteioles different in diameter

Answer 23

When the afferent arteriole is larger, more blood would flow into the efferent arteriole, which is of a smaller diameter, resulting in increased blood pressure in the glomerulus

Question 24

glomerular filteration

Answer 24

a) four pressures (define each) involved in the process

1 Glomerular blood hydrostatic pressure (GBHP) is the blood pressure in glomerular capillaries. Generally, GBHP is about 55 mmHg. It promotes filtration by forcing water and solutes in blood plasma through the filtration membrane.

2 Capsular hydrostatic pressure (CHP) is the hydrostatic pressure exerted against the filtration membrane by fluid already in the capsular space and renal tubule. CHP opposes filtration and represents a “back pressure” of about 15 mmHg.

3 Blood colloid osmotic pressure (BCOP), which is due to the presence of proteins such as albumin, globulins, and fibrinogen in blood plasma, also opposes filtration. The average BCOP in glomerular capillaries is 30 mmHg.

4. Net filtration pressure (NFP) the total pressure that promotes filtration, is determined as follows: Net filtration pressure (NFP) = GBHP − CHP − BCOP

b) direction in which each pressure causes fluid to move

from an area of high to low pressure

c) two pressures causing fluid to move out of glomerulus

glomerular hydrostatic pressure, net pressure

d) two pressures causing fluid to move into glomerulus

bcop, chp

e) two combined pressures which exert the greater force

glormerular hydrostatic pressure will

f) resulting effect on glomerular filtration

a pressure of only 10 mmHg causes a normal amount of blood plasma (minus plasma proteins) to filter from the glomerulus into the capsular space

Question 25

how substances are reabsorbed in the nephron

Answer 25

**a) glucose** glucose is reabsorbed in the proximal convoluted tubule (PCT) through the brushboarder, it uses a Na-glucose symporter, and then through the membrane, by a glucose facilitated diffusion transporter **b) amino acids** amino acids are usually flitered out by the use of cotransports which tipichly happen in the proximal convoluted tubule (PCT) **c) water** aquaporins are used to diffuse water throuughout the nephron **d) bicarbonate ions** bicarbonate ions are usually combined and spilt to be able fliter out in varies of cotransporters and pumps

Question 26

obligatory water reabsorption

Answer 26

**a) a definition of the process** where water movement is unpreventable **b) the area of the nephron in which the process occurs** PCT and desending limb on nephron **c) the electrolyte/solute distribution and membrane properties responsible for obligatory water reabsorption** there are aquaporins found in the membrane, as well as many soultes will find their way back to the blood plasma, and since there is a higher concentration in the blood, water will follow **d) the approximate percentage of water reabsorbed by this method** 90%

Question 27

facultative water reabspotion

Answer 27

**a) a definition of the process** it is optional and on a as needed basis, if theres low blood volume or pressure **b) the area of the nephron in which the process occurs** occurs mainly in collecting ducts **c) the electrolyte/solute distribution and membrane properties responsible for facultative water reabsorption** if there is low pressure of blood volume, there will likely be need of/ more water reabsorption **d) the hormone and its action that is responsible for facultative water reabsorption** ADH stimulates exocytosis of aquaporins when needed **e) the approximate percentage of water reabsorbed this method** 10%

Question 28

State the relationship between the thick ascending limb of the loop of Henle and facultative water reabsorption.

Answer 28

This type of water reabsorption occurs in the proximal convoluted tubule and the descending limb of the nephron loop because these segments of the nephron are always permeable to water which makes it obilgatory. 90% of the water is reabsorptioned by the end of the nephron loop

Question 29

**Differentiate between the average amount of filtrate formed per minute and the average amount of urine leaving the kidney per minute**

Answer 29

Nearly about 8 liters for filtrate is formed in a day but only 1-1.5 liter is excreted in form of urine **because of re absorption and secretion process**

Question 30

urine

Answer 30

**a) amount excreted in 24 hours** One to two liters in 24 hours; varies considerably. **b) clarity** Transparent when freshly voided; becomes turbid (cloudy) on standing. **c) colour** Yellow or amber; varies with urine concentration and diet. Color due to urochrome (pigment produced from breakdown of bile) and urobilin (from breakdown of hemoglobin). Concentrated urine is darker in color. Color affected by diet (reddish from beets), medications, and certain diseases. Kidney stones may produce blood in urine. **d) odour** Mildly aromatic; becomes ammonia-like on standing. Some people inherit ability to form methylmercaptan from digested asparagus, which gives characteristic odor. Urine of diabetics has fruity odor due to presence of ketone bodies.

Question 31

chemical comspoition of urine

Answer 31

**a) percentage of water** 95% **b) three most abundant organic solutes** such as fatty acids, pigments, enzymes, and hormones **c) four most abundant inorganic solutes** filtered and secreted electrolytes that are not reabsorbed, urea (from breakdown of proteins), creatinine (from breakdown of creatine phosphate in muscle fibers), uric acid (from breakdown of nucleic acids), urobilinogen (from breakdown of hemoglobin) **d) pH range** Ranges between 4.6 and 8.0; average 6.0; varies considerably with diet. High-protein diets increase acidity; vegetarian diets increase alkalinity

Question 32

specific gravity of urine

Answer 32

**a) a definition of specific gravity** Specific gravity (density) is ratio of weight of volume of substance to weight of equal volume of distilled water. **b) the normal laboratory value** In urine, 1.001–1.035. The higher the concentration of solutes, the higher the specific gravity.

Question 33

**Define the term “micturition”.**

Answer 33

the process of emptying urine from the storage organ

Question 34

mechanisms of micturition

Answer 34

**a) volume of urine which initiates the process** When the volume of urine in the urinary bladder exceeds 200–400 mL, **b) location and type of receptors involved** pressure within the bladder increases considerably, and stretch receptors in its wall transmit nerve impulses into the spinal cord. **c) location and function of the micturition reflex center** These impulses propagate to the micturition center in sacral spinal cord segments S2 and S3 and trigger a spinal reflex called the micturition reflex. **d) nature of the motor pathway to the detrusor muscle and internal sphincter and their responses.** parasympathetic impulses from the micturition center propagate to the urinary bladder wall and internal urethral sphincter. The nerve impulses cause contraction of the detrusor muscle and relaxation of the internal urethral sphincter muscle. **e) nature of the motor pathway to the external sphincter and its response.** Simultaneously, the micturition center inhibits somatic motor neurons that innervate skeletal muscle in the external urethral sphincter. On contraction of the urinary bladder wall and relaxation of the sphincters, urination takes place **f) role of the cerebral cortex** the cerebral cortex can initiate micturition or delay its occurrence for a limited period.

Question 35

1 RENAL CORPUSCLE

Answer 35

Glomerular filtration rate: 105–125 mL/min of fluid that is isotonic to blood Filtered substances: water and all solutes present in blood (except proteins) including ions, glucose, amino acids, creatinine, uric acid

Question 36

2 PROXIMAL CONVOLUTED TUBULE

Answer 36

**Reabsorption (into blood) of filtered:** Water 65% (osmosis) Na+ 65% (sodium–potassium pumps, symporters, antiporters) K+ 65% (diffusion) Glucose 100% (symporters and facilitated diffusion) Amino acids 100% (symporters and facilitated diffusion) CI– 50% (diffusion) HCO3 – 80–90% (facilitated diffusion) Urea 50% (diffusion) **Secretion (into urine) of:** H+ variable (antiporters) Ca2+, Mg2+ variable (diffusion) NH4 + variable, increases in acidosis (antiporters) Urea variable (diffusion) Creatinine small amount At end of PCT, tubular fluid is still isotonic to blood (300 mOsm/liter).

Question 37

3 NEPHRON LOOP

Answer 37

**Reabsorption (into blood) of:** Water 15% (osmosis in descending limb) Na+ 20–30% (symporters in ascending limb) K+ 20–30% (symporters in ascending limb) CI– 35% (symporters in ascending limb) HCO3 – 10–20% (facilitated diffusion) **Secretion (into urine) of:** Urea variable (recycling from collecting duct) At end of nephron loop, tubular fluid is hypotonic (100–150 mOsm/liter).

Question 38

4 EARLY DISTAL CONVOLUTED TUBULE

Answer 38

**Reabsorption (into blood) of:** Water 10–15% (osmosis) Na+ 5% (symporters) CI– 5% (symporters) Ca2+ variable (stimulated by parathyroid hormone)

Question 39

5 LATE DISTAL CONVOLUTED TUBULE AND COLLECTING DUCT

Answer 39

**Reabsorption (into blood) of:** Water 5–9% (insertion of water channels stimulated by ADH) Na+ 1–4% (sodium–potassium pumps and sodium channels stimulated by aldosterone) Urea variable (recycling to nephron loop) **Secretion (into urine) of:** K+ variable amount to adjust for dietary intake (leakage channels) H+ variable amounts to maintain acid–base homeostasis (H+ pumps) Tubular fluid leaving the collecting duct is dilute when ADH level is low and concentrated when ADH level is high.