Urinary System

Paired organs that produce urine

Behind abdominal peritoneum (posterior)

Kidneys

Stores and eliminates urine

Urinary tract

Paired tubes which takes urine from each kidney to the urinary bladder (posterior)

Ureters

Muscular sac for temporary urine storage

Urinary bladder

Tube that takes urine from the bladder to the outside

*One

Urethra

Which structure pushes right kidney down?

Liver

Another term for urination?

Micturition

The process of eliminating urine

Contraction of this forces urine through urethra, and out of body

Urination

Muscular urinary bladder

Function of urinary system:

Removal of metabolic wastes from body fluids

Excretion

Function of urinary system:

Discharge of wastes from the body

Elimination

Functions of urinary system:

Regulation of BV and BP

Regulates the plasma concentration of ions

Helps stabilize pH

Conserves nutrients

Assists the liver in detoxifying poisons

Homeostatic regulation

The kidneys are held in position by what?

Peritoneum, contact with adjacent visceral organs, and supporting connective tissues

Connective tissue around kidney that is the layer of collagen fibers that cover the outer surface of the entire organ

Fibrous capsule

Connective tissue around kidney that is the thick cushioning layer of adipose tissue surrounding the fibrous capsule

Perinephric fat

Connective tissue around kidney that is the dense, fibrous outer layer that anchors the kidney to surrounding structures

Renal fascia

Prominent medial indentation that serves as point of entry for the renal artery and nerves and exit for the renal vein and ureter

Hilum

Internal cavity within kidney

What tissue is it lined by?

What tissue does it contain?

Renal sinus

Fibrous capsule lining

Contains adipose tissue, and the urine collecting ducts and chambero

Superificial region of kidney

Renal cortex

Extension of renal cortex with bands of tissue that extend into renal medulla, between renal pyramids

Renal columns

Inner region of kidney

Renal medulla

Triangular structures in the medulla

Renal pyramids

Tip of renal pyramids projecting into renal sinus

Renal papilla

Consists of a renal pyramid, the overlying area of the renal cortex, and adjacent renal columns

Kidney lobe

Cup-shaped drain that collects urine from ducts that converge at the renal papilla of each renal pyramid

Minor calyx

Larger passageway formed by four or five minor calyces merging together

Major calyx

Large, funnel-shaped chamber formed from the merger of the major calyces

Fills most of renal sinus

Drains urine into ureter

Renal pelvis

Kidneys receive what percent of the total cardiac output

20-25%

How much blood (in mL0 flows through the kidneys each minute?

1200mL

Each kidney receives blood through what?

Renal artery

The renal artery branches into what?

Segmental arteries

The segmental arteries divide into what, which pass through the renal columns

Interlobar arteries

Interlobar artieries supply blood to where, which arch along the boundary between the cortex and the renal pyramids

Arcuate arteries

The arcuate arteries give rise to multiple of these to radiate into the cortex

Cortical radiate artery (interlobular artery)

These branch from each cortical radiate artery and deliver blood to capillaries supplying individual nephrons

Multiple afferent arterioles

These drain blood from smaller venules and deliver blood to the arcuate veins

Cortical radiate veins (interlobular veins)

These veins empty into interlobar veins, there are no segmental veins

Arcuate veins

What innervation does most of the work for the kidneys by adjusting the rate of urine formation by changing blood flow at the nephron

It influences urine composition by stimulating the release of renin

Sympathetic innervation

These innervate the kidneys and ureters

Renal nerves

This is the microscopic functional unit of the kidneys

What begins here?

Empties into the ___________

Nephron

Urine production

Empties into the collecting system

This is responsible for filtering blood that gets pushed out and it consists of:

• Glomerular (Bowman’s) capsule - filtration occurs

• Glomerulus (capillary network)

Renal corpuscle

This is a long passageway and it consists of:

•Proximal convoluted tubule

•Nephron loop (Loop of Henle)

•Distal convoluted tubule

Renal tubule

Which has a larger diameter? The afferent or efferent arteriole?

Afferent

Forms the outer wall of the corpuscle

• Containing glomerular capillaries

What are the 2 layers?

Glomerular capsule

Capsular outer layer + visceral layer

Simple squamous epithelium that forms the outer wall

Capsular outer layer

Layer of specialized cells that cover the glomerular capillaries

Visceral layer

Space between capsular outer layer and visceral layer where filtrate collects

Capsular space

Large specialized cells of the visceral layer with foot processes (pedicels) that wrap around the glomerular capillaries

Podocytes

Narrow gaps between the adjacent foot processes of podocytes

Filtration slits

The glomerulus is a ball of about how many intertwined capillaries?

50

Blood is delivered to the glomerulus by what artieroles?

Blood leaves through what?

Afferent

Efferent arterioles

Fenestrated capillaries with large-diameter pores through the endothelium

Glomerular capillaries

Filtration is driven by what?

What is forced out?

Blood pressure

Forces water and small solutes out of the glomerular capillaries and into the capsular space

Filtration produces a solution called what?

Filtrate

Filtration membrane consists of what 3 things?

• Fenestrated endothelium of the glomerular capillaries

• Basement membrane – thin layer of extracellular matrix

• Filtration slits between foot processes of podocytes

This is proximal to the renal corpuscle (first segment)

Its wall is made of this epithelium with microvilli on the apical surface

Think of it like a strainer

Proximal convoluted tubule (PCT)

Made up of simple cuboidal epithelium

Taking things from blood, through interstitial fluid, through tube, and into filtrate

Takes things from tubular fluid to blood

Secretion

Reabsorption

Three processes of renal tubule?

Filtration —> Reabsorption —> Secretion

U-shaped segment that extends at least partially into the medulla of the kidney

Neprhon loop (loop of Henle)

Descending thin limb (DTL) of squamous epithelium

Ascending thin limb (ATL) of squamous epithelium and thick ascending limb (TAL) of cuboidal epithelium

Descending limb

Ascending limh

Distal segment that empties into a collecting tubule

• Initial portion passes between the afferent and efferent arterioles

• Smaller luminal diameter than the P C T

• Cuboidal epithelial cells lack microvilli

Distal convoluted tubule (DCT)

Structure that helps regulate BP and filtrate formation

Juxtaglomerular complex (JGC)

The juxtaglomerular complex (JGC) consists of what 3 things?

Macula densa

Juxtaglomerular cells

Extraglomerular mesangial cells

Specialized epithelial cells of the DCT near the renal corpuscle that can function as chemoreceptors or baroreceptors

Macula densa

Modified smooth muscle cells in the wall of the afferent arteriole that function as baroreceptors and secrete renin

Juxtaglomerular cells

Located in the space between the afferent and efferent arterioles. Provide feedback control between the macula densa and the juxtaglomerular cells.

Extraglomerular mesangial cells

A series of tubes that carries tubular fluid away from the nephrons

Makes final adjustments to the composition of the tubular fluid before it becomes urine

Collecting system

Receives tubular fluid from many nephrons

Begin where and descend where?

Carry tubular fluid into ____, which drains into minor calyx

Collecting ducts

Begin in cortex and descend through medulla

Papillary duct

Reabsorb water and secrete potassium ions

Regulate acid-base balance

Principal cells

Intercalated cells

85% of all nephrons are what?

Where are they located?

Relatively short loop

Efferent arterioles deliver blood to what network?

Cortical nephrons

Located within the cortex

Network of peritubular capillaries

This long nephron loop extends deep into the medulla

Contains vasa recta (long straight capillaries that run parallel to the nephron loop of juxtamedullary nephrons)

Juxtamedullary nephrons

These wastes are excreted in urine

Metabolic wastes

Most abundant organic waste, generated primarily through the breakdown of amino acids

From the breakdown of creatine phosphate

From recycling of nitrogenous bases

Urea

Creatine

Uric acid

Small or large amount of glucose in urine?

Wide range of this in urine and small range in plasma?

Small (large for diabetics)

Sodium

The interlobar veins drain directly into which vein?

The renal vein

Specialized cells derived from smooth muscle, located among glomerular capillaries

• Provide structural support, can control the diameter of the capillaries and perform phagocytosis

Intraglomerular mesangial cells

Blood pressure forces water and solutes across walls of glomerular capillaries and into the capsular space

• Only selective based on size

Filtration

Movement of water and solutes from the filtrate (tubular fluid) to the peritubular fluid and back to blood

Reabsorption

Transport of solutes from blood to the peritubular fluid and into the filtrate (tubular fluid)

Secretion

Glomerular filtration is driven by what?

Hydrostatic pressure

In this process, blood plasma is forced through the filtration membrane and water and small solute molecules pass through, while larger solutes and cells are restricted

Glomerular filtration

The pressure of blood flowing through the glomerular capillaries

Pushes water and solutes out of the blood and into _____

Glomerular hydrostatic pressure (GHP)

filtrate

Why is the hydrostatic pressure in the peripheral capillaries higher?

Because efferent arteriole has a higher resistance than the afferant arteriole

The pressure of the filtrate in the capsular space

Opposes what pressure to push water and solutes out of filtrate and back into blood

Results from the resistance to flow of ______ along the nephron and conducting system

Capsular hydrostatic pressure (CsHP)

Opposes glomerular hydrostatic pressure

Results from resistance to flow of filtrate (urine)

The difference between GHP and CsHP

GHP - CsHP

Net hydrostatic pressure (NHP)

This is the pressure due to the concentration of solute (mostly proteins) in blood. Pulls water and solute back into the glomerular capillaries and opposes filtration

This is the pressure that drives filtration and is the difference between the NHP and the BCOP. NHP-BCOP

Net filtration pressure (NFP)

Amount of filtrate the kidneys produce per minute

What is the average?

Glomerular filtration rate (GFR)

125mL/min

Glomeruli generate about ____ liters of filtrate per day

180

If blood pressure in the glomeruli falls more than 20%, the ____ pressure falls and _____ stops, which can lead to acute kidney failure

net filtration pressure falls

filtration stops

Regulation of GFR in what 3 ways?

1. Autoregulation (local)

2. Hormonal regulation

3. Autonomic regulation (by the nervous system)

Maintains adequate GFR despite changes in local blood pressure and blood flow

Myogenic mechanisms: involve changing the diameter of the afferent arterioles, efferent arterioles and glomerular capillaries

Autoregulation of GFR (intrinsic control)

Activated when the juxtaglomerular complex (JGC) releases renin in response to:

• Low blood pressure (low GFR) at the glomerulus due to decrease in blood volume, decrease in systemic blood pressures, or blockage in the renal artery or its branches

• Stimulation of juxtaglomerular cells by the sympathetic nervous system

• Decrease in osmotic concentration of the tubular fluid at the macula densa (low G F R results in more reabsorption of solute along the tubule)

Renin-angiotensin-aldosterone system (RAAS)

The enzyme renin converts the inactive plasma membrane angiotensinogen to _______________

This new component is converted to ______ by _________

angiotensinogen I —> angiotensin II (by ACE - angiotensin-converting enzyme)

What are the 3 effects of angiotensin II?

Increases blood pressure

• Vasoconstriction in peripheral vessels and constricts the afferent arterioles of the glomeruli

• Increasing cardiac output

Increased fluid retention due to

• Increased aldosterone secretion

• Increased production of ADH

Stimulates thirst centers

Overall effect: Increase in systemic BP and BV and restoration of normal GFR

This is released by the heart in response to increased BV or pressure

Atrial natriuretic peptide (ANP)

What are the 4 effects of ANP?

Dilation of the afferent arterioles and constriction of efferent arterioles of the glomerulus

Decrease in cardiac output and vascular resistance

Increase in glomerular pressures and increase in GFR to quickly reduce blood volume

Decrease sodium reabsorption and water reabsorption (decrease in aldosterone and A D H)

Overall effect: increase in urine production and decrease in blood volume and pressure (and GFR)

This type of activation increases renin release, constrict afferent arterioles, decreases GFR and slows filtrate production, and shunts blood away from the kidneys and to other organs like muscles and skin

Sympathetic activation

What are the 3 functions of the renal tubule?

Reabsorbing all useful organic nutrients from the filtrate

Reabsorbing more than 90% of the water from the filtrate

Secreting any wastes that did not enter filtrate at the glomerulus

4 transport mechanisms of reabsorption and secretion

Diffusion

Osmosis

Leak channels

Carrier-mediated transport

In carrier-mediated transport, a specific substrate binds to a _____ protein that facilitates movement across the membrane (can be active or passive)

Works in one direction only

carrier

The concentration at which the carrier proteins are saturated and cannot transport any more substrate

Transport maximum (Tm)