Anatomy and Cell Biology 3309 Lecture Notes - Lecture 22: Distal Convoluted Tubule, Renal Corpuscle, Proximal Tubule

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tealminnow441

22 May 2018

School

Western University

Department

Anatomy and Cell Biology

Course

Anatomy and Cell Biology 3309

Professor

Martin Sandig

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Histology 3309

Urinary Passages

Learning Objectives

1. describe components, location and function of the juxtaglomerular apparatus

2. prepare a diagram of the renin-angiotensin-aldosterone system

3. compare the epithelial lining and functions of proximal tubule, loop of Henle, and distal tubule

4. describe the location and histology of the renal medulla

5. explain the structure and significance of transitional epithelium

6. outline the histological features of the urinary bladder.

- Podocytes are part of the visceral layer of bowmans capsule adjacent to glomerular capillaries

- The layer continues around at the vascular pole to become the parietal layer of bowmans

capsule

- We also have a urinary space that collects the filtrate and sends it to the proximal convoluted

tubule

- Podocyte organization:

- We have a fenestrated capillary part of the glomerular capillary that form a BM that fuses

together w the BM of the podocyte

- This is a foot process (aka minor pedicel) (aka secondary pedicel) (aka secondary foot process)

- These are held together by filtration slit diaphragm made of nephrin

- Tissue fluid will be sent through this basement membrane and a lot of material will be filtered

out to create an ultrafiltrate within the urinary space

- Recall: basis for filtration: charge and size

The Nephron

- Production of ultrafiltrate from blood

- Conservation of water, electrolytes and metabolites

- Removal of metabolic waste

- The filtrate leaves the urinary space and enters proximal convolute tubule and then it flows the

loop of henle (that enters the medulla) and comes back up to the cortex

o Recall: the loop of henle has both a thick and a thin part

- The filtrate then enters the distal convoluted tubule and then is sent to the collecting tubule,

back into the medulla and out of the kidney

- The purpose of this is to recover a lot of material that has been filtered out (including water)

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- At the end, what we excrete is just metabolic waste

- The proximal convoluted tubule + distal convoluted tubule + renal corpuscle are found in the

cortex

- Distal convoluted tubule:

o Has a well recognizable lumen

- Proximal convoluted tubule:

o Fairly small lumen (sometimes not even visible)

- Most prominent feature of the loop of henle is that part of it is thin (meaning that the epithelial

cells are squamous)

o The cells are squamous and the cytoplasm is very thin

o This allows resorption of water and NaCl through that tuble

- TS = thin segment

o Here the epithelial cells have nuclei that is very prominent but the cytoplasm is very

thin

- VR = vasa recta

o The capillaries that run parallel to the tubules to take in liquid that leaves the epithelial

lined loop of henle into those capillaries

- Collecting duct:

o Cuboidal to low columnar in shape

o Large lumen

- The proximal convoluted tubule resorbs most of the stuff (vitamins, amino acids, glucose, water,

ions, electrolytes etc)

- The filtrate then goes through the loop of henle and 2 things happen:

o The epithelum changes as it goes around the loop

o The descending limb of the loop of henle is freely permeable to water (water can easily

leave the tubule)

o This happesn bc the ascending limb of the loop of heble and the distal convoluted tubule

is IMPERMEABLE to water but it actively pumps out NaCl

o So the cells in the distal convoluted tubule and the ascending limb pump out NaCl

o This creates a high concentration of ions right outside the tubule

o SO water tries to equilibrate that and flows out at the descending limb

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- 2 mechanisms for water regulation:

o aldosterone

▪ hormone

▪ produced by the adrenal gland

▪ regulates NaCl resorption from the tubule cells

▪ this indirectly regulates water reabsorption

o antidiuretic hormone (ADH) (aka vasopressin)

▪ the collecting duct has water channels within the epithelium that can be turned

on and off

▪ through the regulation of these water channels, the water reabsorption can be

regulation

▪ produced in the brain

Juxtaglomerular Apparatus

- the distal convoluted tubule originated from the renal corpuscle

- the distal convoluted tubule comes back to its own renal corpuscle at the vascular pole

- macula densa cells

o bunch of cells located right at the vascular pole

o these cells are bunched together closely (their nuclei are close together) →in light

microscopy, it shows up as a dense spot

o part of the distal convoluted tubule

o these cells measure NaCl

o they measure how efficient reabsorption of NaCl is at that nephron

- this info is conveyed to the juxtaglomerular cells

o specialized smooth muscle cells within the wall of the afferent arteriole

o these cells are both contractile and sympathetic

o JG cells produce renin

▪ Renin is a signalling molecule that starts a cascade of events

- Extraglomerular mesangial cells are also involved in the process of signal transmission bw the

macula densa and the JG cells

o There are gap junctions that are signaling things across

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Document Summary

Podocytes are part of the visceral layer of bowmans capsule adjacent to glomerular capillaries. The layer continues around at the vascular pole to become the parietal layer of bowmans capsule. We also have a urinary space that collects the filtrate and sends it to the proximal convoluted tubule. We have a fenestrated capillary part of the glomerular capillary that form a bm that fuses together w the bm of the podocyte. This is a foot process (aka minor pedicel) (aka secondary pedicel) (aka secondary foot process) These are held together by filtration slit diaphragm made of nephrin. Tissue fluid will be sent through this basement membrane and a lot of material will be filtered out to create an ultrafiltrate within the urinary space. Recall: basis for filtration: charge and size. The filtrate then enters the distal convoluted tubule and then is sent to the collecting tubule, back into the medulla and out of the kidney.

Related Questions

1) Which is NOT characteristic of metabolism during theabsorptive state?

a) oxidation of about 50% of the glucose absorbed from a typicalmeal

b) conversion of glucose to glycogen in hepatocytes

c) gluconeogenesis using amino acids

d) glucose not picked up by the liver is converted intotriglycerides.

e) deamination of absorbed amino acids which enteredhepatocytes.

2) In the Krebs cycle, an oxidation-reduction reaction is likelycoupled with a substrate-level phosphorylation. True or False?

3) Glycolysis is an example of oxidative phosphorylation. trueor false?

4)Which of the following statements is incorrect?

a)In the proximal convoluted tubule, sodium ions are reabsorbedthrough the apical membrane by the Na⁺ -glucosesymporters and Na⁺ /H⁺ antiporters

b) In the loop of Henle, Na⁺-K⁺-2Cl^- Symporters reclaim sodium, potassiumand chloride from fluid in the tubule lumen.

c)In the distal convoluted tubule, sodium resorption is mainlyby osmosis

d) In the collecting duct, principle cells absorb sodium.

5) Which of the following might indicated abnormal kidneyfunction?

a)creatinine clearance less than 120-140 mL/min

b)serum creatinine less than 1.5 mg/dL (135 mmol/liter)

c) glucose in the urine

d) creatinine clearance less than 120-140 mL/min and serumcreatinine less than 1.5 mg/dL (135 mmol/liter) are bothcorrect

e)creatinine clearance less than 120-140 mL/min, serumcreatinine less than 1.5 mg/dL (135 mmol/liter), and glucose in theurine are all correct

6) ACE inhibitors can lower blood pressure because inhibitingACE

a) stops the secretion of renin

b) prevents the formation of angiotensin I

c) prevents the formation of angiotensin II

d)increases the secretion of aldosterone

e)prevents norepinephrine from binding alpha 1 receptors onblood vessels

7) Which of the following statements is TRUE?
1. Hydrogen ions are secreted by Na⁺/H⁺antiporters in the proximal tubules.
2. H⁺ATPases (proton pumps) in the collecting ductssecrete hydrogen ions.
3. Cl^-/HCO₃^- antiporters help withhydrogen ion reabsorption.

8) Which of the following is mismatched?

a)Sodium ions ï¿½ Level is controlled by aldosterone, antidiuretichormone, and atrial natriuretic.

b) Chloride ions ï¿½ Level is controlled by chloride ion leakagechannels and antiporters.

c) Potassium ions ï¿½ Level is controlled by aldosterone.

d) Bicarbonate ions ï¿½ Level is controlled mainly by kidneys.

e) Calcium ions ï¿½ Level is regulated by osmosis.

9) Which of the following statements is correct?

a) In the menstrual phase, follicle stimulating hormonestimulates development of secondary follicles in the ovaries andprostaglandins cause loss of the stratum functionalis.

b)In the preovulatory phase, secondary follicles start tosecrete estrogens and inhibin. One becomes a dominant follicle andsecretes estrogens and inhibin causing decreased FSH secretionleading to atresia of less developed follicles. In the uterus, theendometrium undergoes repair under the influence of estrogens.

c)In ovulation, release of luteinizing hormone causes release ofthe secondary oocyte.

d) In the postovulatory phase, progesterone and estrogens aresecreted by the corpus luteum promote thickening of the endometriumpreparing for implantation. If no pregnancy occurs, progesteroneand estrogen levels drop and menstruation occurs.

e) all of these statements are correct

10)The secretory phase of the uterine cycle is associatedwith

a)increased secretion of progesterone and formation of thecorpus albicans.

b)increased secretion of progesterone and formation of thecorpus luteum.

c) increased secretion of luteinizing hormone and rupture of themature follicle.

d)increased secretion of estrogen and maturation of thesecondary follicle

e) increased secretion of follicle stimulating hormone andovulation.

11) Filtered fluid leaving the glomerular capillariesIMMEDIATELY enters the

a) glormerulus

b) proximal convulted tubule

c) collecting duct

d) glomerular capsule

e) loop of henle

12)Which correctly associates structure with tissue type?

a)PCT: simple cuboidal epithelium consisting of principle cellsand intercalated cells

b)descending limb and thin ascending limb of nephron loop:simple squamous epithelial cells

c) thick ascending limb of nephron loop: simple cuboidalepithelial cells with prominent brush borders of microvilli

d) DCT: simple cuboidal to low columnar epithelial cells

e) collecting duct: stratified cuboidal epithelial cells

13) Regulation of the volume and osmolarity of body fluidsoccurs first in the

a) proximal convoluted tubules.

b) distal convoluted tubules.

c) loop of Henle.

d) glomerular capsule.

e) collecting ducts.

14) Which is NOT True about podocytes?

a) their pedicels form filtration slits

b) they make up the parietal layer of the glomerular capsule

c) they are modified simple squamous epithelial cells

d)all of these choices statements about podocytes are true

15) In the process of forming concentrated urine, symporters inthe loop of Henle cause sodium ions and chloride ions to build upin the renal medulla helping to form the osmotic gradient. ADHincreases reabsorption of water by principal cells in thecollecting ducts.

True or False?

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Anatomy and Cell Biology 3309 Lecture Notes - Lecture 22: Distal Convoluted Tubule, Renal Corpuscle, Proximal Tubule

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