Anatomy and Phyisology Urinary System

Functions of Urinary System:

Excretion, elimination, homeostasis

Excretion:

remove organic waste products from the body

Homeostasis:

Regulation of blood volume, blood pressure, & blood plasma solute composition/concentration (including blood pH)

Parts of the urinary system: (4)

kidney, ureter, urinary bladder, urethra

Makes up the urinary tract: (3)

Ureter, urinary bladder, urethra

Function of kidney in the urinary system:

produces urine; specifically the Juxtamedullary nephron

Function of ureter in the urinary system:

transport urine toward the urinary bladder

Function of urinary bladder in the urinary system:

temporarily stores urine prior to elimination

Function of urethra in the urinary system:

conducts urine to exterior; transports semen in males

Kidneys:

bean shaped, capped by adrenal gland, located on either side of the vertebral column, retroperitoneal, everything enters and exits at the hilum

Entering/exiting at the hilum of the kidneys:

renal artery & nerves GO IN

renal vein & ureter GO OUT

Renal Cortex of the kidneys:

Superficial portion; Extends into the medulla as renal columns

Renal Medulla of the kidneys:

Arranged as triangular sections of tissue deep to the cortex; Triangular sections are called the renal pyramids

Renal Pelvis of the kidneys:

Medullary pyramids drain into calyces that connect to the common drainage area called the renal pelvis; The ureter then takes fluid from the renal pelvis to the urinary bladder

renal pyramids

Triangular sections of the renal medulla portion of the kidneys are called:

Where medullary pyramids drain, and that connect to the common drainage area in the renal pelvis portion of the kidneys:

calyces

Common drainage area in the renal pelvis of the kidneys:

renal pelvis

The ureter takes fluid from the renal pelvis to the ________ ________

urinary bladder

functional unit of the kidneys:

The nephron

Located in the cortex of the kidneys:

nephron

located in renal columns of the cortex of the kidneys:

juxtamedullary nephrons

A nephron consists of:

1) Renal corpuscle

a. glomerulus

b. glomerular capsule

2) renal tuble

A ball of capillaries

glomerulus

Surrounds the capillary ball, creating a space around the glomerulus to collect fluid

Glomerular (Bowman's) capsule

Renal tubule

Proximal convoluted tubule;

Nephron loop (loop of Henle);

Distal convoluted tubule

The distal convoluted tubules empty into collecting ducts in the...

medulla

collecting ducts drain into the....

calyces, then into the renal pelvis

Blood flows into the glomerulus through the...

afferent arteriole (then through the glomerular capillaries)

Blood exits the glomerulus through the...

efferent arteriole

The efferent arteriole branches into a network of...

capillaries that surround the renal tubule

the network of capillaries that surround the renal tubule in the CORTICAL NEPHRONS is called:

peritubular capillaires

the network of capillaries that surround the renal tubule in the JUXTAMEDULLARY NEPHRONS is called:

vasa recta

Urine production: FILTRATION

1. Blood is filtered through the capillaries of the glomerulus

2. Produces a filtrate that collects in the glomerular capsule -- filtrate very similar to plasma

3. filtrate then flows through renal tubule

Urine production: REABSORPTION

1. Mainly occurs in the the proximal convoluted tubules

2. Water and solutes needed by the body are reabsorbed by renal tubule

2. Water and solutes needed by the body are reabsorbed by renal tubule

Urine production: SECRETION

1. Mainly occurs in the distal convoluted tubules

- Especially waste products and drugs

- secrets ions to help regulate pH

Glomerular Filtration Rate (GFR)

amount of filtrate the kidneys produce each minute

Glomerular Filtration Rate (GFR) is determined by the:

balance of the forces pushing fluid out and pulling fluid back into the glomerular capillaries

Blood pressure in the glomeruli

pushes fluid out (hp)

Colloid osmotic pressure (OP) in the capsule

pulls fluid back in

Control of GFR (3)

1. autoregulation

2. autonomic regulation

3. hormonal regulation

Autoregulation of GFR

- Local control of the diameter of afferent and efferent arterioles

- vasoconstriction of AFFERENT arteriole decreases GFR

Vasoconstriction keeps GFR constant by:

The vasoconstriction decreases blood pressure of the blood entering the glomerulus = keeps GFR constant

Autonomic regulation of GFR

-sympathetic nerve innervation

- vasoconstriction of AFFERENT arteriole decreases GFR

Hormonal regulation of GFR

- Renin-Angiotensin System (released by juxtaglomerular complex in response to decrease BP or vol.)

-increases systemic BP to maintain normal GFR

Angiotensin II = vasoconstriction and aldosterone release =

increase in systemic blood

Aldosterone = increased water absorption by kidneys =

increase in systemic BP

water is reabsorbed

all along the renal tubule

occurs in the proximal convoluted tubule & descending limb of the nephron loop

water reabsorption along the renal tubule

The amount of water reabsorbed through the distal convoluted tubules and collecting ducts can be...

modified to produce dilute or concentrated urine, depending on the needs of the body

The DCT and collecting ducts do not absorb water unless:

Anti-diuretic hormone (ADH) is present

increase in ADH = increase in water reabsorption =

increase in urine concentration & decrease in urine vol.

The ureters are:

Muscular tubes that take urine from the renal pelvis to the urinary bladder

Ureters enter the....

posterior bladder wall obliquely (Slit-like openings)

The ureters prevent:

backflow of urine from the bladder into the ureters and kidneys

Oblique entry causes the ureteral openings to be...

closed off automatically when the urinary bladder fills up

The bladder muscle is called

the detrusor muscle

The urinary bladder:

- Distensible, muscular, temporary storage area for urine

- Very small when empty

- Can expand to hold up to a liter of urine

the bladder is lined with:

transitional epithelium

urine exits the bladder through:

internal urethral orifice = controlled by the internal urethral sphincter (involuntary muscle)

Forms the trigone of the bladder:

The openings of the two ureters and the internal urethral orifice

An area of smooth thick mucosa that helps funnel urine out of the bladder:

the trigone of the bladder

takes urine from the bladder to the outside of the body

the urethra

Stretch receptors in the bladder wall are stimulated as the bladder fills with urine

Micturition Reflex

When a signal threshold is reached (about 200-400 ml of urine), parasympathetic signals contract the detrusor muscle and relax (open) the internal urethral sphincter

followed by the voluntary relaxation of the external urethral sphincter