Essentials of Human Anatomy & Physiology

Mr. Hildebrandt

The Urinary SystemAnatomy & Physiology II

Urinary System FunctionsUrinary System Functions Regulates homeostasis:

Water & Electrolytes

Blood pressure & pH

Red blood cell production

Elimination of waste products: Nitrogenous wastes

Toxins

Drugs

Urinary system OrgansUrinary system Organs

Kidneys

Ureters

Urinary bladder

Urethra

The Kidneys The Kidneys Against dorsal body

wall Right kidney is slightly

lower than the left 3 Regions:

Renal cortex – outer region

Renal medulla – inside the cortex

Renal pelvis – inner collecting tube

Kidney CharacteristicsKidney Characteristics Attached to ureters, renal

blood vessels, and nerves at renal hilus

Atop each kidney is an adrenal gland

Renal capsule - Surrounds each kidney

Kidney stones – filtrate concentrates, crystallizes and forms stony masses

UretersUreters Slender tubes attaching the

kidney to the bladder

Continuous with the renal pelvis

Enters posterior portion of the bladder

Runs behind the peritoneum

Peristalsis aids gravity in urine transport

Urinary BladderUrinary Bladder Smooth, collapsible, muscular sac

Temporarily stores urine

UrethraUrethra Thin-walled tube that carries

urine from the bladder to the outside of the body by peristalsis

Release of urine is controlled by two sphincters

Both sphincter muscles must open to allow

micturition (voiding)

Urethra Gender DifferencesUrethra Gender Differences

Function: Females – only carries

urine Males – carries urine &

sperm cells

Length: Females – 3–4 cm (1 inch) Males – 20 cm (8 inches)

Nephrons:Nephrons: filter “junk” out of bloodfilter “junk” out of blood Structural & functional units of kidneys Responsible for forming urine Nephron structures:

Glomerulus Bowman’s capsule Proximal convoluted

tubule Loop of Henle Distal convoluted tubule Collecting duct

Urine Formation ProcessesUrine Formation Processes Filtration - Water and

small solutes (filtrate) are forced out of glomerulus & into Bowman’s capsule

Reabsorption - Blood capillaries reabsorb 99% of water, glucose, amino acids, & ions from renal tubule

Secretion - Hydrogen & potassium move back into renal tubules resulting in urine

Formation of UrineFormation of Urine

Characteristics of UrineCharacteristics of Urine Colored somewhat

yellow due to the pigment urochrome and other solutes

1.8 liters produced per day

Slightly aromatic

pH normally 6ish

Sterile

Maintaining the BalanceMaintaining the Balance Water intake must equal water output

Blood pH must remain between 7.35 and 7.45 to maintain homeostasis

Kidneys increase water volume & sodium in blood to control blood pressure

Kidneys recognize hypoxia (low oxygen levels) & responds:

Erythropoietin is released in blood Bone marrow produces more RBCs