The Excretory System

Functions of the Urinary System Filtration of the blood Occurs in the glomerulus of the kidney nephron Contributes to homeostasis by removing toxins or waste

Urinary System Renal artery Renal Vein Kidney Ureter Urinary Bladder For sphincters, see next slide Unit 1 - Objective 1

Functions of the Urinary System Reabsorption of vital nutrients, ions and water Occurs in most parts of the kidney nephron Contributes to homeostasis by conserving important materials

Urinary System Female Sphincters Male Sphincters Internal urethral sphincter External Urethral Sphincter Unit 1 - Objective 1

Functions of the Urinary System Secretion of excess materials Assists filtration in removing material from the blood Contributes to homeostasis by preventing a build-up of certain materials in the body such as drugs, waste,etc.

Functions of the Urinary System Activation of Vitamin D Vitamin D made in the skin is converted to Vitamin D3 by the kidney Active Vitamin D (D3) assists homeostasis by increasing calcium absorption from the digestive tract Unit 1 - Objective 1

Functions of Kidney Structures The Renal Artery Transports oxygenated blood from the heart and aorta to the kidney for filtration

Functions of Kidney Structures Renal Vein Transports filtered and deoxygenated blood from the kidney to the posterior vena cava and then the heart

Functions of Kidney Structures Nephron The physiological unit of the kidney used for filtration of blood and reabsorption and secretion of materials Unit 1 - Objective 1

Functions of Kidney Structures Capsule The outer membrane that encloses, supports and protects the kidney

Functions of Kidney Structures Cortex The outer layer of the kidney that contains most of the nephron; main site for filtration, reabsorption and secretion

Functions of Kidney Structures Medulla inner core of the kidney that contains the pyramids, columns, papillae, calyces, pelvis and parts of the nephron not located in the cortex; used for salt, water and urea absorption Unit 1 - Objective 1

Functions of Kidney Structures Ureter Transports urine from the renal pelvis to the bladder Unit 1 - Objective 1

Functions of Kidney Structures Renal Pyramids Triangular shaped units in the medulla that house the loops of Henle and collecting ducts of the nephron; site for the counter-current system that concentrates salt and conserves water and urea

Diagram of Kidney Nephron Efferent arteriole Afferent arteriole Bowman’s capsule Collecting duct Proximal convoluted tubule Glomerulus Peritubular capillaries Vasa recta Decending limb of loop of Henle Ascending limb of loop of Henle Distal convoluted tubule

Functions of Nephron Structures Glomerulus The site for blood filtration operates as a nonspecific filter; in that, it will remove both useful and non-useful material the product of the glomerulus is called filtrate

Functions of Nephron Structures Bowman’s Capsule A sac that encloses Bowman’s Capsule and transfers filtrate from the glomerulus to the Proximal Convoluted Tubule (PCT)

Functions of Nephron Structures The primary site for secretion (elimination) of drugs, waste and hydrogen ions Saves water for the body Unit 1 - Objective 1

Site of Filtration Glomerulus the Glomerulus is the site of filtration the filtration mechanism is sieve-like and consists of fenestrated glomerular capillaries, podocytes and a basement membrane that allows free passage of water and solutes smaller than plasma proteins

The Juxtaglomerular Apparatus Used in maintaining blood pressure

Disorders of the Urinary System Renal Calculi (kidney stones) caused by the crystallization of calcium, magnesium or uric acid salts that precipitate in the renal pelvis. If the calculi become large and travel down the ureter, they can cause excruciating pain

Disorders of the Urinary System Cystitis typically caused by bacteria from the anal region, but, can also be caused by sexually transmitted diseases and various chemical agents can lead to inflammation, fever, increased urgency and frequency of urination and pain

Disorders of the Urinary System Glomerulonephritis ( Bright’s Disease) caused by inflammation of the glomeruli due to an abnormal immune response (autoimmune, streptococcal antibody complexes). Inflammation of the glomeruli leads to faulty filtration (passage of blood cells and proteins) and possible kidney failure.

Disorders of the Urinary System Incontinence caused by loss of the ability to control voluntary micturition (releasing urine from the bladder) due to age, emotional disorders pregnancy, damage to the nervous system, stress, excessive laughing and coughing leads to wetting of clothing, discomfort and embarrassment Unit 1 - Objective 1

Dialysis Therapy Dialysis is a process that artificially removes metabolic wastes from the blood in order to compensate for kidney (renal) failure. Kidney failure results in the rapid accumulation of nitrogen waste (urea, etc.) which leads to azotemia. Uremia and ion disturbances can also occur. This condition can cause acidosis, labored breathing, convulsions, coma and death.

Dialysis Therapy The most common form of dialysis is hemodialysis which uses a machine to transfer patient’s blood through a semipermeable tube that is permeable only to selected substances.

Dialysis Therapy Some key aspects of hemodialysis are: - blood is typically transferred from an arm artery - after dialysis, blood is typically returned to an arm vein - to prevent clotting, blood is typically heparinized - dialysis sessions occur about three times a week - each dialysis session can last four to eight hours! - long term dialysis can lead to thrombosis (fixed blood clots), infection and death of tissue around a shunt (the blood access site in the arm)

Source: Modified from Robert F. Allen