Urinary System

Functions of Urinary System Filter Blood Regulation of Blood Volume/Pressure Regulation of the solute concentration of the Blood pH regulation of extracellular fluid Regulation of RBC synthesis [erythropoietin] Vitamin D activation

Anatomy of the Urinary System

Kidneys Primary organs of the urinary system Located between the 12 th thoracic and 3 rd lumbar vertebrae. Right is usually lower due to liver. Held in place by connective tissue [renal fascia] and surrounded by thick layer of adipose [perirenal fat]

Kidneys Renal Arteries carry 15-30% of total cardiac output to the kidneys.

Ureters Each ureter is about 25 cm (10 in.) long and carries urine from the renal pelvis to the urinary bladder via peristaltic waves. Valve-like flap of internal mucous membrane covers bladder opening one way flow of urine into the bladder

Review Draw a rough diagram of a kidney. Label the: Cortex Medulla Pelvis How is the composition of the ureter similar to the composition of the alimentary canal? How is it different?

Bladder The Urinary Bladder is a ‘temporary storage’ reservoir for urine. Empty = in pelvis Full = above the symphysis pubis Urethral sphincter: band of muscles encircling the opening to the urethra.

Bladder Layers 1.Mucous Coat Folds called rugae Thickness of this tissue changes as the bladder expands and contracts 2.Submucous coat Elastic connective fibers 3.Muscular coat Detrusor muscle 4.Serious coat Connective tissue

Bladder Is it really an emergency to leave class in order to micturate (pee)? 150mL – urge to urinate 300mL – intense sensation to urinate 600mL – sensation of pain So next time you need to leave class, you are to take a 500mL water bottle. If its full when you come back then you don’t have to stay after class. (lol jk jk)

Urethra thin walled tube – conveys urine from bladder to external environment. Similar structure to ureter Sphincters: internal urethral [involuntary] & external urethral [voluntary] Male Urethra 20 cm long [7-8 in] Transports both urine & semen Eternal urethral orifice opens at tip of penis Female Urethra 3-4 cm long [1.5 in] External urethral orifice opens just anterior to the vaginal opening

Micturition (Urination) External urethral sphincter controls urination Voluntary skeletal muscle Under constant contraction Urination occurs when muscle relaxes At least 500 mL (17 oz) of urine must be eliminated every day removes potential toxic materials from the body. A normal adult eliminates from 1.5 L (1.6 qt) to 2.3 L (2.4 qt) of Urine a DAY (depending).

Review 1.Write two “quiz” questions about information we’ve discussed so far 2.See if your neighbor can answer the questions. 3.If they can’t, explain the answer to them.

Nephrons Each kidney contains over a million nephrons [functional structure] Blood enters the nephron from a network that begins with the renal artery. This artery branches into smaller and smaller vessels – and enters each nephron as an afferent arteriole.

Nephrons The afferent arteriole enters the Glomerular Capsule (Gomerulus).

Nephrons Blood leaves through the smaller efferent ateriole Passes through the peritubular capillaries (remember for later) Leaves the kidneys through the renal veins

Nephron

1) Glomerular Filtration Fluid diffuses from the high pressure afferent arteriole to the low pressure Bowman’s Capsule Glomerular filtrate in proximal convoluted tubule (PCT) similar to plasma H 2 O, Na +, Cl -, glucose, amino acids, Ca +, Mg +, K +, micronutrients [zn, cu, fe] Urea & Creatinine

1) Glomerular Filtration Affect Filtration Rate Change in pressure vasoconstriction / vasodialation of arterioles Increase / decrease in blood pressure Solute concentration More proteins = less osmosis Regulating Filtration Rate Sympathetic nervous system Alters blood pressure Renin Enzyme secreted by the juxtaglomerular cells to constrict efferent arteriole.

2) Tubular Reabsorption Where’s it Reabsorbed? From the [high concentration] Proximal Convoluted Tubule & Loop of Henle To [low concentration] peritubular capillaries What’s Reabsorbed? Active Transport Glucose Amino Acids Acids Ascorbic, lactic, citric, etc. Ions P, S, Ca, K, Na Osmosis/Diffusion Water

3) Tubular Secretion Active transport of substance in blood to renal tubules Penicillin, histamine, phenobarbital, H +, K +, ammonia. In Distal Convoluted Tubule and Collecting Duct

Excretion Highly inefficient Urine H 2 O Urea Creatinine Ammonia Uric Acid Oxalate Na +, Cl -, K +, H +, HCO 3 - (small amounts)

Review Label where the three steps of urine formation occur in the nephron Glomerular filtration Tubular Reabsorption Tubular Secretion Draw a rough diagram of a nephron. (see on right)

Kidney Stones Statistics: Kidney stones affect more than a million Americans each year Twelve to 24 million Americans will develop stones in their lifetime There are approximately 350,000 new stone cases reported each year. In the United States, 7 to 10 of every 1,000 hospital admissions are due to kidney stones.

Kidney Stones (Calculi) Mineral salt crystals that precipitate from urine. Small as a grain of sand Large as a golf ball. The size, shape, and location of the stone can cause many different symptoms. Most are extremely small and pass through without any symptoms Large calculi can obstruct renal ducts or the ureters. Causes severe pain.