Urinary System Anatomy Practical [PHL 212]

When protein is broken down in the body, it results in nitrogenous waste that must be eliminated from the body All 20 amino acids have a amino group (NH 2 ). When broken down for energy, the amino group is converted to ammonia (NH 3 ). Ammonia is converted into urea by the liver. Urea is then transported in the blood to the kidneys where the urea is removed from the blood. Urea is less toxic than ammonia and can be transported in the blood to the kidney Urinary System

Functions of the Urinary System Kidneys carry out four functions  Filter nitrogenous wastes, toxins, ions, etc. from blood to be excreted as urine.  Regulate volume and chemical composition of blood (water, salts, acids, bases).  Produce regulatory enzymes.  Renin – regulates BP/ kidney function  Erythropoietin – stimulates RBC production from marrow.  Metabolism of Vitamin D to active form.

Organs of the Urinary system Two Kidneys: Perform all functions except actual excretion. Two Ureters: Convey urine from Kidneys to Urinary Bladder Urinary Bladder: Holds Urine until excretion Urethra: Conveys urine from bladder to outside of body

Kidneys Anatomy  Average size – 12cm x 6cm x 3 cm  Weights 150 grams  Lie against posterior abdominal wall at level of T12-L3.  The right kidney is slightly lower than the left due to the shape of the liver.  Attached to ureters, renal blood vessels, and nerves at renal hilus  At the top of each kidney is an adrenal gland

Kidney- External Anatomy  Lateral surface- convex  Medial is concave- ◦ Renal Hilum  Opening to Kidney ◦ Renal Sinus  Space within hilus  Kidneys receive blood vessels and nerves.

Kidney Structures  Renal cortex – outer region  Renal medulla – inside the cortex  Renal pyramids – triangular regions of tissue in the medulla  Renal columns – extensions of cortex-like material inward  Calyces – cup-shaped structures that funnel urine towards the renal pelvis  Renal pelvis – inner collecting tube

Nephrons  The structural and functional units of the kidneys  1 million per kidney  Responsible for urine formation  Main structures of the nephrons  Glomerulus  Renal tubule

Types of Nephrons  Cortical nephrons  Located entirely in the cortex  ~85% of all nephrons  Juxtamedullary nephrons  Found at the boundary of the cortex and medulla

Glomerulus  A specialized capillary bed  Attached to arterioles on both sides (maintains high pressure)  Large afferent arteriole  Narrow efferent arteriole  The glomerulus sits within a glomerular capsule (the first part of the renal tubule)

Renal Tubule  Glomerular (Bowman’s) capsule  Proximal convoluted tubule  Loop of Henle  Descending limb  Ascending limb  Distal convoluted tubule

Ureters  Slender tubes attaching the kidney to the bladder  Continuous with the renal pelvis  Enter the posterior aspect of the bladder  Peristalsis aids gravity in urine transport

Urinary Bladder  Smooth, collapsible, muscular sac  Temporarily stores urine  Trigone – three openings  Two from the ureters & One to the urethrea

Urethra  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  Internal urethral sphincter (involuntary)  External urethral sphincter (voluntary)

Urethra Gender Differences  Length  Females – 3–4 cm (1 inch)  Males – 20 cm (8 inches)  Location  Females – along wall of the vagina  Males – through the prostate and penis  Function  Females – only carries urine  Males – carries urine and is a passageway for sperm cells