Introduction to Urinary System PDF

Urinary system To filter out cellular wastes, toxins and excess water or nutrients from the circulatory system Involved in fluid balance, electrolyte balance and excretion of urine. Includes kidneys, ureters, urinary bladder and urethra Kidney Ureter Urinary bladder Urethra URINARY SYSTEM PARTS AND...

Urinary system To filter out cellular wastes, toxins and excess water or nutrients from the circulatory system Involved in fluid balance, electrolyte balance and excretion of urine. Includes kidneys, ureters, urinary bladder and urethra Kidney Ureter Urinary bladder Urethra URINARY SYSTEM PARTS AND FUNCTIONS Two kidneys The kidneys remove urea from the blood through tiny filtering units called nephrons. Urea, together with water and other waste substances, forms the urine as it passes through the nephrons and down the renal tubules of the kidney. Two ureters. These narrow tubes carry urine from the kidneys to the bladder. Muscles in the ureter walls continually tighten and relax forcing urine downward, away from the kidneys. If urine backs up, or is allowed to stand still, a kidney infection can develop. About every 10 to 15 seconds, small amounts of urine are emptied into the bladder from the ureters. Bladder. This triangle-shaped, hollow organ is located in the lower abdomen. It is held in place by ligaments that are attached to other organs and the pelvic bones. The bladder's walls relax and expand to store urine, and contract and flatten to empty urine through the urethra. The typical healthy adult bladder can store up to two cups of urine for two to five hours. -Two sphincter muscles. These circular muscles help keep urine from leaking by closing tightly like a rubber band around the opening of the bladder. -Nerves in the bladder. The nerves alert a person when it is time to urinate, or empty the bladder. Urethra. This tube allows urine to pass outside the body. The brain signals the bladder muscles to tighten, which squeezes urine out of the bladder. At the same time, the brain signals the sphincter muscles to relax to let urine exit the bladder through the urethra. When all the signals occur in the correct order, normal urination occurs. Kidney Pair of excretory organs lie on the posterior abdominal wall (retroperitoneal organs), on either side of vertebral column Removes waste products of metabolism and excess of water & salts from blood and maintains its pH They extend from upper border of 11th thoracic vertebra to the 3rd lumbar vertebra Right kidney is slightly lower than the left due to the presence of liver Left kidney is longer and narrower than the right Inferior vena cava Right kidney Ureter Left suprarenal gland Abdominal aorta The kidney is a bean shaped organ It has 2 poles, 2 borders and 2 surfaces 2 poles: - Upper & lower poles Upper pole broader, close contact with adrenal gland Lower pole pointed Upper pole 2 borders: – Lateral & medial borders Lateral border is convex Medial border is concave, presents hilum The hilum transmits renal vein, renal artery & renal pelvis Lateral border 2 surfaces: Anterior & posterior surfaces Anterior surface is irregular and convex Posterior surface is flat Lower pole Relations of the kidney Anterior relations of the right kidney: - Liver, duodenum Anterior relations of the left kidney: - Pancreas, stomach, spleen Posterior relations of right and left kidneys: - Diaphragm, psoas major, quadratus lumborum and transversus abdominis muscles Coverings of kidney Kidney has 4 coverings, from inside to out they are Fibrous capsule - fibrous membrane closely covering the kidney. Perirenal fat - layer of adipose tissue outside the fibrous capsule, thick at the borders Renal fascia – made up of loose connective tissue o It has anterior and posterior layers o Anterior layer covers the anterior surface o Posterior layer covers the posterior surface o Superiorly 2 layers enclose the suprarenal gland & continue with fascia covering inferior surface of diaphragm o Inferiorly 2 layers enclose the ureter Pararenal fat – layer of fatty tissue lying outside the renal fascia. Thick at the posterior aspect and lower pole of kidney Renal fascia Pararenal fat Perirenal fat Fibrous capsule Structure of kidney Interior of the kidney has cortex, medulla & renal sinus Renal sinus is the space having branches of renal artery, tributaries of renal vein & renal pelvis Renal sinus also contains 2 to 3 major calyces and 10 to 12 minor calyces Medulla is made up of pyramid shaped structures called renal pyramids. Apex of each renal pyramid projects into the minor calyx Cortex lies between the renal pyramids and also covers the base of renal pyramids The cortex and medulla contain about 3 million nephrons Nephron Cortex Medulla Nephron Nephron is the functional unit of the kidney It has 2 parts – renal corpuscle and renal tubule Renal corpuscle: is the part of the nephron where blood plasma is filtered - has following parts Glomerulus – network of blood capillaries Bowman’s capsule Renal tubule: is the part of nephron into which the glomerular filtrate passes - has following parts Proximal convoluted tubule Loop of Henle – descending and ascending limbs Distal convoluted tubule Distal convoluted tubules open into the collecting tubules which open into collecting ducts Nephron Renal Corpuscle Star shaped lumen Very similar to proximal convoluted tubule Has simple cuboidal epithelium, shorter than those of Proximal convoluted tubule. Blood supply of kidney: Arterial supply: Renal artery from abdominal aorta Accessory renal arteries are present in 30% of the individuals. At the hilus renal artery divides into anterior & posterior divisions which later divide into segmental arteries. The segmental arteries are end arteries and supply vascular segments of the kidney Segmental artery divides into lobar arteries Lobar artery divides into interlobar arteries Interlobar arteries divide into arcuate arteries which give interlobular arteries Afferent arterioles for glomerulus arise from interlobular arteries Venous drainage: Renal vein – drain into inferior vena cava Lymphatic drainage: Lateral aortic lymph nodes Nerve supply: By renal plexus composed of sympathetic & parasympathetic Sympathetic fibers are derived from T10-L1 and are vasomotor Parasympathetic are derived from vagus - They secrete renin which increases Na+ reabsorption, increases blood volume, increases constriction of blood vessels, increases blood pressure