HUMB1001 Lecture Notes - Lecture 6: Distal Convoluted Tubule, Proximal Tubule, Renal Function

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How the kidneys regulate body fluid volume and composition

The Renal System

❖ Is part of the urinary system: kidneys, ureters, urinary

bladder & urethra

❖ Kidneys filter the blood but return most of the water &

solutes back to the body

❖ Waste (urine) flows from each kidney, down its ureter to

the bladder (temporarily stored)

❖ Passed to the exterior via urethra

Internal Anatomy of the Kidney

❖ Regions of the kidney:

o Renal cortex

o Renal medulla

o Inner portion consisting of 8-18

cone-shaped renal pyramids separated by

renal columns

o Renal papillae point toward centre

of kidney (renal sinus)

o Drainage system fills the central cavity

o This is known as the renal sinus:

▪ Cuplike structures (minor calyces) collecting

urine from the papillary ducts

▪ Minor and Major calyces empty into the

renal pelvis

▪ The renal pelvis is the expanded end of the

ureter

The Nephron

❖ Renal corpuscle: site of plasma filtration:

o Glomerulus

o Boa’s apsule

❖ Renal tubule:

o Proximal convoluted tubule

o Loop of Henle

o Distal convoluted tubule

❖ Collecting ducts & papillary ducts drain urine to the

renal pelvis & ureter

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“tructure of Bowa’s capsule

❖ Boa’s apsule surrouds the apsular spae otaiig the gloerulus:

o Simple squamous cells from parietal later of capsule

o Podocytes cover glomerular capillaries to form the visceral layer

❖ Glomerular capillaries arise from afferent arteriole before emptying into efferent arterial

Filtration Membrane

1. Fenestrated endothelium (glomerulus)

2. Basement (dialysing) membrane

3. Podocyte cell layer (filtration slits)

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The Glomerulus: Adaption for filtration

1. Tremendous capillary length in the glomerulus

2. Filtration membrane design: Fenestrae → filtrations slits

3. Thin wall (<0.1�m)

4. ↓ efferet arteriole diaeter ireases filtratio pressure

The Nephron

Proximal Convoluted Tubule:

❖ Lies in the cortex

❖ Cuboidal epithelium with microvilli

❖ Cells packed with mitochondria

❖ Very active cells

Loop of Henle:

❖ Cortical Nephrons (80%): short loops

❖ Juxtamedullary Nephrons (20%): long loops

o Descending & ascending limbs

o thik & thi segets

o asa reta

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Document Summary

How the kidneys regulate body fluid volume and composition. Is part of the urinary system: kidneys, ureters, urinary bladder & urethra. Kidneys filter the blood but return most of the water & solutes back to the body. Waste (urine) flows from each kidney, down its ureter to the bladder (temporarily stored) Inner portion consisting of 8-18 cone-shaped renal pyramids separated by renal columns. Renal corpuscle: site of plasma filtration: glomerulus, bo(cid:449)(cid:373)a(cid:374)"s (cid:272)apsule. Renal tubule: proximal convoluted tubule, loop of henle, distal convoluted tubule. Collecting ducts & papillary ducts drain urine to the renal pelvis & ureter. Bo(cid:449)(cid:373)a(cid:374)"s (cid:272)apsule surrou(cid:374)ds the (cid:272)apsular spa(cid:272)e (cid:272)o(cid:374)tai(cid:374)i(cid:374)g the glo(cid:373)erulus: simple squamous cells from parietal later of capsule, podocytes cover glomerular capillaries to form the visceral layer. Glomerular capillaries arise from afferent arteriole before emptying into efferent arterial. The glomerulus: adaption for filtration: tremendous capillary length in the glomerulus, filtration membrane design: fenestrae filtrations slits, thin wall (<0. 1m, effere(cid:374)t arteriole dia(cid:373)eter (cid:894)i(cid:374)(cid:272)reases filtratio(cid:374) pressure(cid:895)

Related Questions

. The kidneys contain millions of _________, which are the smallest functional units of the kidneys since each one can make urine from blood.

2. There are 3 stages in urine formation. The first stage is called____________; during this stage, blood pressure pushes water and small solutes out of a ball of capillaries called the __________ into the first part of the renal tubule called the _________ _________.

3. The second stage of urine formation is called _________. Cells lining the proximal convoluted tubules (PCTs) have special projections called _________ which increase their surface area, thus enabling the PCTs to transport about 70% of filtrate back into blood.

4. When a person is dehydrated, their blood volume and blood pressure are too low. Two hormones reduce the loss of sodium and water from the body during dehydration by concentrating urine to prevent further water loss. The first hormone is secreted by the adrenal cortex and is called __________; this hormone stimulates sodium retention by nephrons. The second hormone is released by the posterior pituitary gland and is called _________; this hormone cause water retention by nephrons.

5. ___________is the waste product of cellular respiration (ATP synthesis). This waste product must be eliminated from the body because it becomes toxic at high levels. This waste product combines with water in blood to form carbonic acid, which is then converted into bicarbonate ions (HCO3-) and hydrogen ions (H+). Hydrogen ions lower blood pH, causing it to become too acidic. Kidneys are able to sense high H+ levels in blood and actively transport hydrogen ions (and other toxic blood borne chemicals) from blood into urine during ___________, the third stage of urine formation.

6. Urine and blood differ in composition. In a healthy person, blood contains _________ , __________, and _________ but urine DOES NOT these materials.

7. Urine moves from the kidneys down the ureters into the bladder due to __________, a form of motility wherein _________ muscle tissue in the ureteral walls undergoes rhythmic waves of contractions.

8. The kidneys are located in the ___________ cavity; ureters conduct urine to the urinary bladder which is located in the pelvic cavity behind the symphysis joint of the _________ bones.

9. The three major systems which participate in the excretion of cellular wastes from blood include: the __________ system which eliminates urea and excess electrolytes like sodium; the ___________ system which eliminates water and salt; and the ____________ system, which eliminates carbon dioxide.

10. When the bladder is full, the _____________ reflex is initiated. During this reflex, the bladder walls contract and the ________ ________ sphincter, a circular structure made of _______ ______tissue, relaxes. Upon sensing an urge to urinate, a person can consciously contract their _______ _______ sphincter, a circular structure made of ________ ________ tissue - this stops the flow of urine out of the bladder and into the urethra until the time is convenient to urinate.

REFERENCE CITATIONS: _______________________________

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HUMB1001 Lecture Notes - Lecture 6: Distal Convoluted Tubule, Proximal Tubule, Renal Function

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