Chapter 29 - Urinary System

Excretory passages - share similar basic structural features (5)

Calyces Pelvis Ureter Urinary bladder Urethra

The epithelial cells of the smaller collecting tubules are

cuboidal

Only ___ cells are present in collecting ducts - deeper in the medulla

Light/principal cells

Int he cortex and in the outer zone of the medulla contain cells (2)

Light/principal cells Dark/intercalated cells

Is a special region of the DCT in which the cells are thickened and narrower

Macula densa (Juxtaglomerular complex)

Is located close to the afferent and efferent arterioles, at vascular pole of renal corpuscle

Macula densa (Juxtaglomerular complex)

Juxtaglomerular Complex (2)

Macula densa Juxtaglomerular cells

Extend into the cortex and alternate with regions of convoluted tubules and renal corpuscles in the cortex

Medullary rays

The parallel bundles of straight tubules are the

Medullary rays

Also play a role in modulating blood flow by contracting in response to angiotensin stimulation (thereby decreasing blood flow)

Mesangial cells

May unclog and recondition the glomerular basement membrane by phagocytosing and removing accumulated filtration residues

Mesangial cells

Provide further support for renal corpuscle

Mesangial cells

Compression of capillaries

Mesangial glomerulonephritis

Deposition of immune complexes in the mesangium

Mesangial glomerulonephritis

Proliferation of mesangial cells

Mesangial glomerulonephritis

Vascular pole of the renal corpuscle

Mesangium

Urine first empties from the renal papilla into the

Minor calyces

Continuous with visceral layer, which is composed of highly specialized epithelial cells called podocytes

Parietal layer (Renal Corpuscle)

Is a simple squamous epithelium

Parietal layer (Renal Corpuscle)

Also adhere closely to the basal lamina that separates the visceral layer of the glomerular capsule from the endothelial layer of the fenestrated glomerular capillaries

Pedicels (of neighboring podocytes) (Renal Corpuscle)

Interdigitate forming slit-like pores between them

Pedicels (of neighboring podocytes) (Renal Corpuscle)

Common cause of nephrotic syndrome in children

Podocyte abnormalities

Loss of foot process

Podocyte abnormalities

Loss of polyanionic charge

Podocyte abnormalities

Form cellular extensions that branch into foot like processes called pedicles

Podocytes (Renal Corpuscle)

Made up of nephrons and collecting tubules (2)

Renal cortex Renal medulla

Contains connecting and collecting tubules and collecting ducts

Renal medulla

Each medullary ray is located at the center of a lobule, flanked by regions of convoluted tubules and renal corpuscles

Renal medulla

contains blood vessels

Renal medulla

contains thin ascending and descending limbs of henle

Renal medulla

Excretory Passages include (5)

Calyces Pelvis Ureter Urinary bladder Urethra

Water enters and exits the PCT cells through ___ located in the apical and basolateral plasma membrane

Aquaporins

Distal convoluted tubule connect to ___, which empty into ___

Arched collecting tubules Straight collecting tubules

Interlobar arteries between pyramids dichotomize into ___

Arcuate arteries

Muscularis propria - The lower 1/3 of the ureter contains

(Additional) Outermost longitudinal layer

Nephrons ___ in each kidney

1.3 million

The apex of each papilla is perforated by openings of ___ in the region called the area cribosa

10-25 collecting ducts (Ducts of Bellini)

Collectively, the cortex receives over ___ blood than the medulla

10x more

Renal medulla ___ renal pyramids

12-15

Renal medulla apex of ___ renal pyramids form a renal papilla

2-3

Mucosa Transitional epithelium ___ layers in the calyces ___ layers in the ureter ___ layers in the bladder

2-3 4-5 6-8

Each minor calyx drains into ____, which in turn drain into the ___

2-3 major calyces Renal pelvis

Renal sinus contains ___ minor calyces and ___ major calyces

7-13 2-3

Obliteration of capillary lumens in

Acute glomerulonephritis

Acute inflammation of the glomerulus

Acute nephritic syndrome

Leads to constriction of blood flow through the kidney

Acute nephritic syndrome

Leads to decrease glomerular filtration rate

Acute nephritic syndrome

Leads to elevated BUN

Acute nephritic syndrome

Leads to hematuria, albuminuria and edema

Acute nephritic syndrome

Leads to increased BP

Acute nephritic syndrome

Leads to leakage of red cells and some protein into urine

Acute nephritic syndrome

Leads to swelling of the endothelium

Acute nephritic syndrome

Loosely arranged CT, with many blood vessels

Adventitia (Excretory Passages)

In the ureter and bladder, the outer layer is ___ in some regions and ___ in other regions

Adventitia Serosa

___ arterioles have a larger diameter than the ___ arteriole

Afferent Efferent

Divide to form a tuft of capillaries, the glomerulus, closely associated with the renal (Bowman's) capsule

Afferent arterioles

Pass through Mesangium (2)

Afferent glomerular arterioles Efferent glomerular arterioles

Mutations in type IV collagen compromise the structure of the basal lamina

Alport syndrome (Renal Corpuscle)

Renal failure is a consequence, because of the abnormal filtration function of the glomerular basal lamina

Alport syndrome (Renal Corpuscle)

Functions as a size and charge (due to heparin sulfate proteoglycans) barrier

Basal lamina (Renal Corpuscle)

Is composed of a network of type IV collagen and laminin, with associated heparin sulfate proteoglycans

Basal lamina (Renal Corpuscle)

Is the critical barrier between the endothelium and the capsular space

Basal lamina (Renal Corpuscle)

Connecting tubule merge to form

Collecting ducts

open into the cribriform area at the apex of the medulla

Collecting ducts

Positioning of the Distal tubule close to the renal corpuscle creates an opportunity for

Communication

Between structures affecting the initial stage of fluid processing and structures at nephron end positions

Communication (Distal Tubule)

From several nephrons merge to form

Connecting tubule

Short segment linking the nephron to the collecting ducts

Connecting tubule

Extend between the pyramids

Cortical columns

Basal plasma membrane forms inholdings that contain the Na+/K+ ATPase

Cuboidal PCT cells

Have a prominent apical brush border formed by the long microvilli that greatly increase the surface area active in reabsorption

Cuboidal PCT cells

Have many mitochondria which reflects the energy requirements of the active transport

Cuboidal PCT cells

Have numerous endocytic vesicles at the bases of apical microvilli, organized in apical canaliculi, which endocytose the small amount of protein remaining in the ultrafiltrate

Cuboidal PCT cells

Lysosomes digest the endocytose proteins

Cuboidal PCT cells

Regulate acid-base balances through the active transport of hydrogen ions

Dark/intercalated cells

Basement membrane is thickened 3-5 times

Diabetes mellitus

Demarcation of lamina lost

Diabetes mellitus

Endstage renal disease: glomerular tuft -> acellular hylanized mass

Diabetes mellitus

Kimmesteil-Wilson nodules

Diabetes mellitus

Mesangial cells produce excess amounts of extracellular matrix

Diabetes mellitus

Histologically very similar (2)

Distal Tubule Distal Convoluted Tubule

Inholdings of the basolateral surfaces (2)

Distal Tubule Distal Convoluted Tubule

Nuclei protrude toward apical lumen (2)

Distal Tubule Distal Convoluted Tubule

Numerous mitochondria, mostly basally located (2)

Distal Tubule Distal Convoluted Tubule

Some cells have irregular microvilli, while others are smooth-surfaced (2)

Distal Tubule Distal Convoluted Tubule

Distal/ascending thin limb of the loop of Henle continues in the cortex as the

Distal convoluted tubule

Thick straight part ascending from the loop of Henle back into the cortex

Distal tubule

Transitional epithelium ___ state - surface cells become squamous to low to cuboidal in shape

Distended (Stretched) (Excretory Passages)

Blood leaves the glomerular capillaries via

Efferent arterioles

Break up into the peritubular capillary plexus networks that surround and supply their own uriniferous tubules

Efferent arterioles (of the cortical nephrons)

The thickness of the three layers of the wall gradually increases down the urinary tract

Excretory Passage

Move urine from the kidney to the outside

Excretory Passages

Mucosa of the urinary bladder forms folds

Excretory Passages

Excretory Passages Mucosa - Lamina propria

FIbroelastic CT

Renal Corpuscle - Form the filtration membrane barrier (3)

Fenestrated capillary endothelium Glomerular basal lamina Slit diaphragm (between pedicles)

Renal corpuscle (2)

Glomerulus Glomerular capsule

Renal corpuscle comprises (2)

Glomerulus Glomerular capsule

Kidneys (2)

Hilum Renal sinus

Is a convex depression in its medial border

Hilum of the kidney

Where branches of the renal artery and nerves enter into the renal sinus

Hilum of the kidney

Where renal vein, lymph vessels and renal pelvis leave the kidney

Hilum of the kidney

Involved in water reabsorption

Light/principal cells

Muscularis Propria in the top 2/3 of the ureter (2)

Inner longitudinal layer Outer circular layer

Afferent glomerular arterioles

Interlobular arteries

Arcuate arteries go into ___

Interlobular arteries

Run in the cortex

Interlobular arteries

Some terminal branches -> Perforating radiate arteries which supply the renal capsule

Interlobular arteries

Drain into arcuate veins

Interlobular veins

Joined by venous ends of peritubular capillary plexus and spending vasa recta

Interlobular veins

Mesangial cells (2)

Intraglomerular Extraglomerular

Are located between the endothelial cells of the glomerular capillaries and cover the capillary surfaces not covered by podocyte processes

Intraglomerular mesangial cells

In contact with the basal portion of the macula dense cells of the DCT, and with the intimal of the arteriole suggesting cellular communication here

Juxtaglomerular cells (Juxtaglomerular complex)

Modified smooth muscle cells in the wall of the afferent arteriole that produce and secrete renin

Juxtaglomerular cells (Juxtaglomerular complex)

the ___ nephrons have longer thin limbs than the ___ nephrons

Juxtamedullary (15%) Cortical

Are bean-shaped organs covered by a thin, fibrous CT capsule

Kidneys

In the calyces and pelvis is a thin and predominantly arranged in a circular manner

Muscularis Propria (Excretory passages)

Smooth muscle arranged in bundles separated by fibroblast if CT

Muscularis Propria (Excretory passages)

Thicker and stronger in the bladder

Muscularis Propria (Excretory passages)

Dense bundles of circular smooth muscle forms the internal urethral sphincter around the neck of the bladder

Muscularis Propria (Bladder)

Middle layer is generally thickest

Muscularis Propria (Bladder)

Thicker and stronger

Muscularis Propria (Bladder)

Three layers are poorly distinguished

Muscularis Propria (Bladder)

Causes structural and functional abnormality of basement membrane

Nephrotic syndrome

Deposition of antigen-antibody complexes on basement membrane

Nephrotic syndrome

Lipids are increased in serum and pass into urine

Nephrotic syndrome

Membranous nephropathy

Nephrotic syndrome

Proteinuria, hypoalbuminemia, edema

Nephrotic syndrome

Usually no red cells or decreased GFR

Nephrotic syndrome

Leaky Basement membrane (3)

Nephrotic syndrome Diabetes mellitus Podocyte abnormalities

Excretory Passages Submucosa

None

Renal Corpuscle layers (2)

Parietal layer Visceral layer

Continuous with proximal convoluted tubule at urinary pole, roughly opposite to the vascular pole

Parietal layer (Renal Corpuscle)

In the adult, it forms a continuous smooth outer zone

Renal cortex

Although the nephron provides a continuous, tubular path, the epithelial lining changes abruptly for each segment

Proximal convoluted tubule

Are the longest segment of the nephrons in the cortex and fill most of the cortex

Proximal convoluted tubule

Can be distinguished as the microvillar debris remains in the lumen

Proximal convoluted tubule

Microvilli of the apical brush border are often destroyed as a result of post mortem degeneration

Proximal convoluted tubule

The simple squamous lining of the parietal layer of Bowman's capsule quickly transitions at the proximal convoluted tubule to a cuboidal epithelium with an extensive apical brush border

Proximal convoluted tubule

Renal tubules (6)

Proximal convoluted tubule Proximal straight tubule Loop of Henle Distal straight tubule Distal convoluted tubule Connecting tubule

Have a shorter straight part that enters the renal medulla

Proximal convoluted tubules

In medullary rays have prominent apical microvilli brush border

Proximal straight tubules

The ultra filtrate flows from the ___ in the medullary ray into the medulla

Proximal straight tubules

The ultra filtrate passes from the PCT into the ___ in medullary rays, in the cortex

Proximal straight tubules

Transitional epithelium ___ state - surface cells are dome shaped and balloon into the lumen of the organ

Relaxed (Excretory Passages)

Also contains mesangial cells

Renal Corpuscle

Bowman's capsule is a double-walled epithelial cup

Renal Corpuscle

Fluid under pressure moves from the circulation and across the filtration membrane barrier to enter the capsular space

Renal Corpuscle

Has a vascular pole and tubular (urinary) pole

Renal Corpuscle

A funnel-shaped, expanded part of the ureter

Renal Pelvis

Each nephron comprises (2)

Renal corpuscle Renal tubules

Renal cortex contain (7)

Renal corpuscles Proximal convoluted tubules Distal convoluted tubules Distal tubule Cortical connecting tubules Cortical collecting tubules Blood vessels

Between the renal capsule and the renal medulla

Renal cortex

Forms projections called cortical columns

Renal cortex

Contains infrarenal part of renal pelvis

Renal sinus

Contains perirenal fat

Renal sinus

Contains segmental and lobar branches of the renal artery

Renal sinus

Is lined by the renal fibrous capsule which is continuous with the adventitia of minor renal calyces

Renal sinus

Arcuate veins -> Interlobar veins united to form ___ -> ___

Renal veins IVC

Are modified and specialized tight junctions composed of nephrins, glycoproteins and proteoglycans

Slit diaphragms (Renal Corpuscle)

Span adjacent pedicles and bridge the slit-like pores

Slit diaphragms (Renal Corpuscle)

Collect blood from the fibrous renal capsule

Stellate veins

Collect blood from the most superficial zone of renal cortex

Stellate veins

Drain into interlobular veins

Stellate veins

Are initially in medullar rays in the cortex

Straight collecting tubules

Continue down through the medulla, ending in the large, straight, papillary ducts that open at the apex of the renal papilla in the area cribosa

Straight collecting tubules

Has a simple squamous epithelium that is thin, but not as thin as a capillary wall

Thin limb of loop of Henle

Apical cytoplasm contains an abundant micro filaments and reserve membrane in vesicles

Transitional epithelium (Excretory Passages)

Appear to have four to six layers in the contracted or relaxed state

Transitional epithelium (Excretory Passages)

When distended, the reserve membrane is used to expand the apical surface as the cells flatten

Transitional epithelium (Excretory Passages)

Urinary system includes (4)

Two Kidneys Two Ureters One bladder One urethra

Control of acid-base balance

Urinary System (Functions)

Control of blood volume and blood pressure

Urinary System (Functions)

Elimination of foreign substances and their breakdown products

Urinary System (Functions)

Excretion of waste products of metabolism

Urinary System (Functions)

Maintenance of extracellular fluid volume

Urinary System (Functions)

Metabolism of vitamin D

Urinary System (Functions)

Production of renin

Urinary System (Functions)

Regulates the volume and composition of body fluids

Urinary System (Functions)

Regulation of body water

Urinary System (Functions)

Regulation of erythropoisis

Urinary System (Functions)

Regulation of salts, retained or excreted

Urinary System (Functions)

In the absence of ADH, collecting ducts are impermeable to water, causing the excreted urine to be dilute, or hypotonic

Water permeability

The collecting tubules are involved in the concentration of urine, and are responsive to antidiuretic hormone

Water permeability

The permeability barrier continues in the distal thick limb

Water permeability

The permeability properties reflect the presence or absence of water channels/aquaporins

Water permeability

The thin ascending limb is impermeable to water, although salts can move across the tubule membranes

Water permeability

Water and salts move freely across the membranes of thin descending limb

Water permeability

Efferent arterioles from juxtamedullary nephrons branch into thin blood vessels, the ___

descending vasa recta

At some point after descending the proximal thin limb loops and continues back up as the ___ of the ___

distal (ascending) thin limb loop of Henle

Consequently, the ___ offers greater resistance and contributes to maintaining high blood pressure in the glomerular capillary bed

efferent arteriole

Lobar arteries divides into 2 ___

interlobar arteries

___ of the thin loop directly correlated with the ability to concentrate and produce hypertonic urine

length

Segmental arteries go to the ___

lobar arteries

In the medulla vasa recta are structured into bundles in close association with the ___ and ___

loops of Henle Collecting ducts

Descending vasa recta branch into ___, and then return as ___

peritubular capillary networks ascending vasa recta

The ultra filtrate passes from the proximal straight tubules in medullary rays, in the cortex into ___ down though the outer stripe of the outer medulla

proximal thick, descending limb

Blood enters each kidney through the ___ and goes to ___

renal artery segmental arteries

Each renal pyramid capped by cortical tissue forms a

renal lobe

As the straight collecting tubules process toward the deeper parts of the medulla and the papilla, they become increasingly ___ cells

taller columnar

varies considerably in length

thin limb

The thick limb changes abruptly to the ___ of the ___ at the inner stripe of the outer medulla

thin limb loop of Henle

The ___ draining the kidney shave no segmental organization like the ___

veins arteries