The Urinary System Chapter 18 Day 1 kidney structure

Urinary System Urinary system is the “sanitary engineer” of the body, it removes the unwanted waste materials and recycling other materials. Functions – Excretion – remove metabolic wastes, toxins, excess ions, and water – Regulate fluid and electrolyte levels – Regulate blood pressure – Transport or store urine

Organs – Filter kidneys (functions 1, 2, 3) – Transport of store urine ureters, urinary bladder, urethra (function 4)

Kidney Structure Location – lie against posterior abdominal wall behind the peritoneum – Retroperitoneal External structure – Size of your fist – Shape of a kidney bean – Concave surface to midline

Supported by three layers of connective tissue – Renal fascia – anchors each kidney – Adipose capsule to cushion – Renal capsule to protect Concave margin of each kidney is hilium – Renal artery, renal vein, and ureter unite with kidney

Internal Structure Three distinct regions Renal pelvis Renal medulla Renal cortex

Renal sinus is the space (basin) of renal pelvis. Calyces are the funnel shaped channels that empty urine into renal pelvis 1. renal pelvis

2. Renal medulla Renal pyramids are darker and striped looking. Renal columns are a lighter area between pyramids.

3. Renal cortex Lighter area of the outer edge Blood supply to and from kidney – renal artery and renal vein 1200 ml every minute is filtered

2/10/2016 Day 2: kidney's nephron structure

Nephron Structure Functional subunit of kidney – Million in each kidney – Microscopic in size but extends from medulla to cortex Two parts – Renal corpuscle – Renal tubule

Renal corpuscle – bulb-like end of nephron – made up of Bowman’s capsule and Glomerulus Blood plasma filters out of capillary network and into a bowl-like structure that captures plasma

Renal corpuscle Bowman’s capsule – bowl like structure Glomerulus – ball of capillaries with large pores called fenestrae

Renal tubule Long tube where materials can be absorbed or secreted Sections of tubule- proximal convoluted tubule loop of Henle descending limb ascending limb distal convoluted tubule collecting duct

Blood flow Through the Nephron Afferent arteriole Glomerulus Efferent arteriole Peritubular capillaries surrounding the renal tubules Venules

Juxtaglomerular Apparatus Area where distal convoluted tubule and afferent arteriole contact each other Area regulates the rate of urine formation and blood pressure

Kidney Functions Urine Formation – out of the 1200ml of blood that passes into the glomeruli each minute, 120 ml is pushed through renal tubules 180 liters a day!! 99% of this fluid is returned to bloodstream 1% is excreted as urine (1 to 2 liters)

2/10/2016 Day three: Three processes of urine formation and maintenance of body fluids

3 processes of urine formation- 1.Glomerular filtration – movement of blood plasma and small substances through the filtration membrane barrier by net filtration pressure material entering the Bowman’s capsule is called filtrate. Blood cells, large molecules such as proteins cannot move through

Rate of filtration is determined by amount of filtration pressure. Volume increases, pressure increases, urine volume increases

2. Reabsorption – return of water and other substances from the filtrate within the renal tubules into the peritubular capillaries. proximal convoluted tubules are most active segment in reabsorption. 99% of water, essentially all of the nutrients, and many essential ions

3. Secretion drugs, hydrogen ions, potassium ions, penicillin, uric acid and urea move from peritubular capillaries into renal tubules by active transport, diffusion, or facilitated diffusion depending upon material. blood pH is controlled by adjusting quantity of hydrogen ions secreted

Urea and uric acid formation are nitrogen- containing waste products resulting from metabolism They can cause serious damage and are life- threatening. Kidneys remove urea and uric acid on a continuous basis

Regulation of urine concentration and volume fluctuate in response to changing conditions of the body. Extra salt – urine output greater with high salt content Heavy exercise – urine output less with less salt content There are several other factors that control urine output; enzymes, hormones and nervous impulses

Maintenance of Body Fluids Kidneys are primary organs in the body that regulate the water-salt balance of all body fluids in all body compartments. Regulation of pH by – Buffers – accept or release hydrogen ions – most important buffer - bicarbonate system – Respiratory System – change in ventilation rate and depth can adjust carbon dioxide levels, and therefore pH levels – Kidneys – remove excess hydrogen ions in the blood by secretion

Ureters – Paired tubular organs that transport urine from the kidneys to urinary bladder Mucus protects inner lining Muscle layer undergoes peristaltic contractions

Urinary Bladder – – Hollow, muscular organ located at floor at floor of pelvic cavity – Trigone – triangular region that receives the openings from the ureters and the urethra – Four layers which include a mucous membrane and layer of muscle. Urethra – – Muscular tube that carries urine from urinary bladder to the outside

Micturition – – Act of emptying the bladder is initiated by the activation of stretch receptors on the wall of the bladder – Internal sphincter relaxes, muscle contracts and if the voluntary sphincter relaxes, urine flows out