THE URINARY SYSTEM

Functions of the Urinary System

1. Regulation of blood volume and pressure

2. Regulation of electrolyte levels

3. Regulation of acid-base balance

4. Removal of metabolic wastes and toxins

5. Regulation of red blood cell production (erythropoiesis)

6. Activation of vitamin D for calcium absorption

lined with

transitional epithelium

Organs of the Urinary System

Kidneys, ureters, urinary bladder, urethra

Location of the kidneys

Located on either side of the vertebral column, retroperitoneal, against the back muscles, near the lower ribs

renal artery associated with each kidney

(brings oxygenated blood to the kidney)

renal vein associated with each kidney

(carries deoxygenated blood away from the kidney)

Renal capsule

Fibrous covering surrounding the kidney

Renal cortex

Outer region of the kidney, contains nephrons and blood vessels

Renal medulla

Inner region of the kidney, consists of renal pyramids

Renal pyramids

Triangular-shaped structures within the renal medulla, contain nephron loops

Renal papilla

Tip of the renal pyramid where urine is collected

Renal pelvis:

Funnel-shaped structure that collects urine from the calyces

Renal calyces

Cup-shaped structures that collect urine from the renal papillae

Ureter

Tube that carries urine from the kidney to the urinary bladder

Functional unit of the kidney

Nephron

Microscopic structures of a nephron

Renal corpuscle: Consists of Bowman's capsule and glomerulus

Bowman’s (glomerular) capsule

Cup-shaped structure surrounding the glomerulus

Glomerulus

Network of capillaries where blood filtration occurs

Renal tubule

Consists of proximal convoluted tubule, loop of Henle, and distal convoluted tubule

Proximal convoluted tubule

Site of reabsorption of water and solutes from the filtrate

Loop of Henle

U-shaped portion of the nephron, involved in water and electrolyte reabsorption

Distal convoluted tubule

Site of further reabsorption and secretion

Collecting duct

Collects urine from multiple nephrons and carries it to the renal pelvis

Blood circulation through the kidneys and nephrons

Renal artery and renal vein: Supply and drain blood from the kidneys

Afferent arterioles

Bring blood to the glomerulus

Glomerulus

Site of blood filtration

Efferent arterioles

Carry blood away from the glomerulus

Peritubular capillaries

Surround the renal tubules, involved in reabsorption and secretion of substances

Filtration

The process by which blood is filtered in the renal corpuscle, allowing water and small solutes to pass into the renal tubule

Reabsorption

The process by which substances such as water, glucose, and electrolytes are reabsorbed from the renal tubules into the bloodstream.

Secretion

The process by which substances such as hydrogen ions, potassium ions, and drugs are actively transported from the bloodstream into the renal tubules for excretion

Location and function of the juxtaglomerular apparatus

1. Location: Found near the glomerulus of the nephron, where the afferent arteriole enters and the distal convoluted tubule begins.

2. Function: Regulates blood pressure and the filtration rate of the glomerulus through the release of renin, which helps control blood pressure, and the production of erythropoietin, which stimulates red blood cell production.

Structure and function of the ureters

1. Structure: Long muscular tubes that extend from the kidneys to the urinary bladder, consisting of smooth muscle layers for peristaltic contractions.

2. Function: Transport urine from the kidneys to the urinary bladder via peristaltic waves, preventing backflow of urine.

Location, structure, and function of the urinary bladder

1. Location: Located in the pelvic cavity, posterior to the pubic symphysis.

2. Structure: Hollow muscular organ with elastic walls that expand to store urine, and contract to expel urine during urination.

3. Function: Stores urine until it is expelled from the body during micturition (urination).

Structure and function of the male urethra

Longer tube that extends from the urinary bladder through the penis, serving as a passageway for both urine and semen during ejaculation.

Structure and function female urethra

Shorter tube that extends from the urinary bladder to the external urethral orifice, serving solely as a passageway for urine to exit the body.