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Copyright © 2011 Pearson Education, Inc.

The Urinary System:Chapter 24


Chapter 24 Overview

Kidney Anatomy

Gross

Microscopic

Nephrons


Urinary System Organs

• Kidneys

• Major filter organs

• Ureters

• Connect kidneys to bladder

• Urinary bladder

• Urine holding tank

• Urethra

• Exit tube


Kidney Function

• Filters blood

• Removes toxins

• Metabolic wastes, excess ions from the blood

• Regulates blood chemistry

• Volume

• Composition (electrolytes)

• pH

• Endocrine function

• Erythropoetin production


Kidney Location

• Retroperitoneal

• Superior lumbar region

• Right kidney lower than left

• Convex lateral surface, concave medial surface

• Medial renal hilum

• Ureters, renal blood vessels, lymphatics, and nerves enter and exit


Kidney Anatomy

Layers of supportive tissue

1. Renal fascia

• Anchors kidney

2. Perirenal fat capsule

• fatty cushion

3. Fibrous capsule

• Adheres to kidney

• Prevents spread of infection


Internal Kidney Anatomy

• Three regions

1. Cortex

2. Medulla

3. Pelvis


Renal Cortex

• Superficial region of kidney

Renal medulla

• Cone-shaped “renal pyramids”

• Separated by renal columns, form lobes

• Produce urine

• Empty into minor calyces


Renal Pelvis

• Funnel-shaped tube

• Continuous with the ureter

• Formed from minor calyces major calyces



• Three regions

1. Lobe

2. Papilla

3. Minor calyces


Internal Anatomy

• Lobe

• Pyramid and surrounding tissue

• Papilla

• Tip of pyramid


Internal Anatomy

• Major calyces

• Branching channels of renal pelvis

• Collect urine from minor calyces

• Empty urine into the pelvis

• Urine flows from the pelvis to ureter

Copyright © 2011 Pearson Education, Inc. Figure 24.3

Renal cortex

Renal medulla

Major calyx

Papilla ofpyramidRenal pelvis

Ureter

Minor calyx

Renal column

Renal pyramid in renal medulla

Fibrous capsule

Renalhilum

(a) Photograph of right kidney, frontal section (b) Diagrammatic view



Blood Supply

• Aorta renal artery

• Renal artery… nephron blood vessels

• Afferent arteriole

• Glomerulus

• Efferent arteriole

Copyright © 2011 Pearson Education, Inc. Figure 24.4b

Aorta

Renal artery

Segmental artery

Interlobar artery

Arcuate artery

Cortical radiate artery

Afferent arteriole

Glomerulus (capillaries)

Nephron-associated blood vessels(see Figure 24.7)

Inferior vena cava

Renal vein

Interlobar vein

Arcuate vein

Cortical radiatevein

Peritubularcapillaries

and vasa recta

Efferent arteriole

(b) Path of blood flow through renal blood vessels


Blood Supply

• Renal arteries deliver blood

• ~ 1/4 (1200 ml) of cardiac output per minute

• All blood travels through glomerulus

• Filter structure

• Renal veins carry blood away


FUNCTIONAL UNITS OF THE KIDNEY:NEPHRONS


Nephrons

• Structural units, form urine

• ~1 million per kidney

Two main parts

1. Glomerulus: a group of capillaries

2. Renal tubule: process and filter urine

• Glomerular capsule

• Convoluted tubule

Copyright © 2011 Pearson Education, Inc. Figure 24.5

Nephrons


Nephrons• Renal corpuscle

• Glomerulus + glomerular capsule

• “Baseball + glove”

• Glomerular capillaries are fenestrated

• Allows material to pass

• Surrounded by podocytes


Renal Tubule

• Proximal convoluted tubule (PCT)

• Cuboidal cells with dense microvilli and large mitochondria

• Functions in reabsorption and secretion

• Confined to the cortex


Renal Tubule

• Loop of Henle

• descending and ascending limbs

• Freely permeable to water


Renal Tubule

• Distal convoluted tubule (DCT)

• Function to secrete

• Confined to the cortex

• Empties into the collecting duct


Collecting Ducts

• Receive filtrate from many nephrons

• Fuse together to form minor calyces

• Help maintain water and salt balance


Nephron


Nephrons

Two types

1.Cortical nephrons —85% of nephrons; almost entirely in the cortex

2.Juxtamedullary nephrons

• Long loops of Henle

• deeply invade medulla

• Production of concentrated urine


Nephron Capillary Beds

1. Glomerulus

• Afferent arteriole glomerulus efferent arteriole

• Specialized for filtration – fenestrated

• High pressure


Nephron Capillary Beds

2. Peritubular capillaries

• Formed from efferent arterioles

• Low-pressure

• For absorption

• Cling to renal tubules

• Empty into venules


Filtration Membrane

• Porous membrane surrounding glomerulus

• Consists of

1. glomerular capillaries

2. glomerular capsule

• (podocytes with foot processes and filtration slits)

3. basement membrane

Copyright © 2011 Pearson Education, Inc. Figure 24.9a

Glomerular capillarycovered by podocyte-containing visceral layer of glomerular capsule

Glomerular capillaryendothelium (podocyte covering and basement membrane removed)

Proximal convolutedtubule

Parietal layerof glomerular capsule

Afferentarteriole

Glomerular capsular space

Fenestrations(pores)

Efferentarteriole

Podocytecell body

Foot processesof podocyte

Filtration slits

Cytoplasmic extensionsof podocytes

(a) Glomerular capillaries and the visceral layer of the glomerular capsule


Filtration Membrane

• Allows passage of water and solutes

• Most ions and salts can pass

• Most proteins too large

• blood cells too large

Copyright © 2011 Pearson Education, Inc. Figure 24.9c

(c) Three parts of the filtration membrane

Fenestration(pore)

Filtrate incapsularspace

Foot processesof podocyte

Filtration slit

Slit diaphragm

Capillary

Filtration membrane• Capillary endothelium• Basement membrane• Foot processes of podocyte of glomerular capsule

Plasma

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