Urinary System I

Question 1

the urinary system

Answer 1

consists of the paired kidneys and ureters, the bladder, and the urethra

Question 2

the kidneys

Answer 2

paired bilateral organs located on the posterior abdominal wall. the ureters are tubes that carry the urine from the kidneys to the urinary bladder
- the kidney is a regulatory organ

Question 3

regulatory functions of the kidney

Answer 3

• filtration: water and solutes in the blood leave the vascular space and enter the lumen of the nephron
• regulation: regulates the balance between water and electrolytes, regulates acid-base balance
• modification: modification of the filtrate through selective resorption and specific secretion by the tubules
• endocrine: kidneys synthesize and secrete erythropoietin (regulates RBC production) and renin (controls blood volume and pressure)

Question 4

gross anatomy of the kidneys

Answer 4

kidneys are composed of an outer renal cortex and an inner renal medulla
- medulla is composed of renal pyramids
- kidneys contain renal columns, which are medullary extensions of the renal cortex between the renal pyramids

Question 5

excretory passages of the kidneys

Answer 5

urine is produced in the kidneys are transported out by the ureter into the bladder through a series of excretory passages
- renal pyramid: urine is produced here
- minor calyx: renal calyces are chambers of the kidney which urine passes through. Minor calyces surround the renal papillae of renal pyramids
- major calyx: formed by the union of the seven minor calyces
- renal papilla: location where the renal pyramids empty urine into the minor calyx
- renal pelvis: two to three major calyces unite to form the enlarged renal pelvis which continues as the ureter
- ureter: eventually drains into the urinary bladder

Question 6

blood supply to the kidney

Answer 6

the arterial supply of blood to the kidneys is substantial and complex
- the renal artery, a branch of the aorta, enters the hilum of the kidney. the renal artery branches into interlobular arteries, which travel between the pyramids through the renal columns
- interlobular arteries branch laterally to form the arcuate arteries, which mark the boundary between the cortex and medulla

Question 7

the nephron

Answer 7

basic structural and functional unit of the kidney
- functions to remove wastes from the blood and balance the constituents of the circulation through the process of filtration, reabsorption, and excretion
- each kidney contains one million nephrons that consist of a simple epithelium along their entire length

Question 8

structural components of the nephron

Answer 8

1. renal corpuscles
2. cortical and medullary tubular system

each nephron consists of a blood supply and a specialized network of ducts called tubules

Question 9

renal corpuscle

Answer 9

filtering component of the nephron
composed of a tuft of high pressure capillaries called the glomerulus, which is surrounded by Bowman’s capsule
- for each nephron, an afferent arteriole feeds a high pressure capillary bed called the glomerulus
- blood is filtered by the glomerulus to produce filtrate, which is caught in Bowman’s space

Question 9

major divisions of the nephron

Answer 9

renal corpuscle, proximal tubules, loop of Henle, and distal tubule, collecting duct

Question 10

glomerulus arteriole supply

Answer 10

interlobular arteries travel through the centre of the cortex, where they give off afferent arterioles, which supply the glomerulus

Question 11

proximal convoluted tubule

Answer 11

continues from Bowman’s capsule
- long twisted tubules fill most of the cortex and the kidney
- lined by tall cuboidal epithelium with a brush border

Question 12

proximal straight tubule

Answer 12

after the proximal convoluted tubule enters the medulla, it becomes the proximal straight tubule
- this segment is continuous with the nephron’s loop of Henle

Question 13

Loop of Henle

Answer 13

U-shaped structure consisting of a thick descending limb, a thick ascending limb, and a thin looped segment (thin limb), which interconnects the two
- the ascending limb of the nephron is straight as it enters the cortex and forms the macula densa, and then becomes twisty as the distal convoluted tubule

Question 14

distal convoluted tubule

Answer 14

short and twisty nephron segment
- empties into the collecting system, which empties into the minor calyx
- has low cuboidal lining with irregularly spaced nuclei

Question 15

collecting system components

Answer 15

consists of the connecting tubule, collecting duct, and papillary duct

Question 16

collecting duct

Answer 16

the last part of each nephron which carries the filtrate into a collecting system that transports it to a minor calyx
- a connecting tubule extends from each nephron, and when several tubules join together, they form collecting ducts
- in the apex of the renal pyramid, several collecting ducts merge and deliver urine to the minor calyx

Question 17

classification of nephrons

Answer 17

there are two types of nephrons in the kidney cortex that are classified based on the location of their renal corpuscles:
- juxtamedullary nephrons
- cortical nephrons

Question 18

juxtamedullary nephrons

Answer 18

have their renal corpuscles located near the junction of the cortex and medulla
- they possess long loops of Henle that penetrate deep into the medulla

Question 19

cortical nephrons

Answer 19

have their renal corpuscles located closer to the outskirts of the cortex
- they have short loops of Henle

Question 20

renal corpuscles composition

Answer 20

at the beginning of each nephron is a renal corpuscle, which is comprised of the glomerulus, housed within the Bowman’s capsule

Question 21

renal corpuscle filtration

Answer 21

filtrate from the blood in the glomerulus is collected in the Bowman’s capsule. the filtrate is then further processed as it travels through the nephron to form urine
- successful filtration depends on the specific flow of filtrate and blood through the renal corpuscle

Question 22

filtrate flow in the renal corpuscle

Answer 22

1. afferent arteriole
2. glomerulus
3. Bowman’s capsule
4. urinary pole
5. efferent arteriole
6. vascular pole

Question 23

filtrate flow in the afferent arteriole

Answer 23

blood enters the glomerulus through the afferent arteriole

Question 24

filtrate flow in the glomerulus

Answer 24

the glomerulus is the capillary bed between the afferent and efferent arterioles
- it is suspended within Bowman’s capsule
- glomerular capillaries filter blood based on particle size

Question 25

filtrate flow in Bowman’s capsule

Answer 25

bowman’s capsule is double walled and encloses the glomerulus. it has an inner visceral layer of podocytes, which surrounds the glomerulus and serves as part of the filtration barrier. the outer parietal layer is simple squamous epithelium, which is continuous with the proximal convoluted tubule
- the glomerular filtrate accumulates between these two layers

Question 26

filtrate flow at the urinary pole

Answer 26

the continuation of the parietal layer of Bowmans capsule, with the epithelium forming the proximal convoluted tubule
- at the urinary pole, the filtrate accumulating in Bowman’s space enters the first tubular part of the nephron, the proximal convoluted tubule

Question 27

filtrate flow at the efferent arteriole

Answer 27

after passing through the renal corpuscle, the capillaries form a second arteriole, the efferent arteriole
- blood exits the glomerulus through the efferent arteriole, which then forms a capillary network around the more distal portions of the nephron

Question 28

filtrate flow at the vascular pole

Answer 28

the junction with the afferent and efferent arterioles is the vascular pole of the renal corpuscle
- the visceral and parietal layers of Bowmans capsule is continuous at the vascular pole

Question 29

the juxtaglomerular apparatus

Answer 29

a regulatory structure formed by the distal convoluted tubule and the afferent arteriole
- located near the vascular pole of the renal corpuscle
- functions to regulate blood pressure and filtration rate

Question 30

juxtaglomerular apparatus composition

Answer 30

• modified cells in the wall of the distal convoluted tubule
• macula densa cells, modified cells in the distal convoluted tubule wall
• juxtaglomerular cells: cells in the wall of the afferent arteriole

Question 31

macula densa cells

Answer 31

modified cells in the wall of the distal convoluted tubule
- monitor sodium concentration in the filtrate, whereas juxtaglomerular cells monitor blood pressure

Question 32

glomerular filtration

Answer 32

involves the transfer of soluble components, such as water and waste, from the blood into the glomerulus
- during filtration, blood enters the afferent arteriole and flows into the glomerulus where filterable blood components (ex: water and waste) will move into bowmans capsule. filterable components accumulate in the glomerulus to form the glomerular filtrate
- non-filterable components (cells and proteins) will exit through the efferent arteriole

Question 33

glomerular filtrate barriers

Answer 33

glomerular filtrate is produced in the corpuscle when blood plasma is forced under pressure through three barriers:
1. fenestrated capillary endothelium
2. glomerular basal lamina
3. filtration slits diaphragms

Question 34

fenestrated capillary endothelium

Answer 34

endothelium of glomerular capillaries is fenestrated with large pores, and these fenestrations block blood cells and platelets
- filtrate is produced in the corpuscles when blood plasma is forced under pressure through the capillary fenestrations, across the filtration membrane surrounding the capillary, and through the filtration slits located between the podocyte pedicels

Question 35

glomerular basal lamina

Answer 35

the pedicels of a podocyte contact the thick, combined basal laminae of the endothelial cell and the podocyte
- the thick combined basal laminae between the podocytes and endothelium restricts large proteins and some organic anions

Question 36

filtration slit diaphragms

Answer 36

filtration slits are the spaces between adjoining pedicels and are spanned by a membrane that also regulate filtration
- restricts some small proteins and organic anions

Question 37

podocytes

Answer 37

each renal corpuscle has a simple squamous parietal layer of the Bowman’s capsule, continuous with the proximal tubule, and a specialized visceral layer of podocytes surrounds glomerular capillaries
- the podocytes, together with the capillary endothelial cells, compose the apparatus for renal filtration

Question 38

nucleus of podocytes

Answer 38

together with the endothelial cells of the glomerular capillary and the glomerular basement membrane, they form a filtration barrier

Question 39

podocytes primary process

Answer 39

podocytes extend large, primary processes that curve around a capillary and extend short, interdigitating secondary processes called pedicels
- between the pedicels are narrow spaces called filtration slits

Question 40

blood supply to the nephron

Answer 40

after passing through the renal corpuscle, the capillaries form a second arteriole, the efferent arteriole
- efferent arterioles will next form a capillary network around the more distal portions of the nephron tubule (the peritubular capillaries and vasa recta) before returning to the venous system
- as the glomerular filtrate progresses through the nephron, these capillary networks recover most of the solutes and water, and return them to the circulation

Question 41

vasa recta

Answer 41

surrounds the loops of Henle, which are located in the medulla of the kidney
- goes into the medullar to approach the loop of Henle

Question 42

peritubular capillaries

Answer 42

tiny blood vessels, supplied by the efferent arteriole that travel alongside the nephrons, allowing reabsorption and secretion between blood and the inner lumen of the nephron
- peritubular capillaries surround the cortical parts of the proximal and distal tubules