Urinary System Guide PDF

Urinary System Guide Introduction I. Function A. Cleaning the blood. B. Making Urine C. Homeostasis 1. Blood Pressure (Blood Volume) 2. Blood pH 3. Electrolyte Balance II. Organs A. Kidney B. Ur...

Urinary System Guide Introduction I. Function A. Cleaning the blood. B. Making Urine C. Homeostasis 1. Blood Pressure (Blood Volume) 2. Blood pH 3. Electrolyte Balance II. Organs A. Kidney B. Ureters C. Urinary Bladder D. Urethra Anatomy of the Kidney I. Cavity/Position A. Each kidney is lateral to the spine between T11 and L3. B. Kidneys are retroperitoneal C. Left kidney is more superior than the right kidney II. Surface Anatomy A. Bean-shaped, brownish in color B. About 4.5-5” in length, approximately the size of a fist. C. Covered by a fibrous renal capsule. D. Anchored to the posterior wall by the renal fascia. E. The adrenal gland sits upon the anterio-medial surface of the kidney. III. Gross Anatomy - Internal A. Renal Cortex - superficial B. Renal Medulla - deep C. Renal Pyramid - A pyramidal-shaped section of the renal medulla 1. Note: While all renal pyramids are part of the renal medulla, not all renal medulla is part of a renal pyramid. D. Renal Column - A portion of the renal cortex that extends between renal pyramids. Allows for the passage of nerves and blood vessels. E. Renal Lobe = Renal Pyramid + Renal Cortex 1. 8-18 renal lobes per kidney  F. Renal Papillae - Tips (Apices) of the Renal Pyramids with openings (from collecting ducts) into the minor calyx. G. Minor Calyx - cup-like structure that receives urine from the renal pyramids via the renal papillae. H. Major Calyx - large cup-like structures that receive urine from minor calyces I. Renal Pelvis - receives urine from the major calyces and sends it to Ureter J. Hilum - Area of entry/exit for Renal Pelvis + Renal Vein + Renal Artery IV. Nervous System/Nerve Supply A. Renal Plexus - describes the nerves that travel into the kidney. B. Efferent Nerves - for sympathetic stimulation of blood vessels = vasoconstriction! C. Afferent Nerves - sensory 1. At T10/T11 level. 2. Dermatome - T10/T11 = lower/mid back pain! Could actually be kidney pain! V. Blood Flow A. Highly vascularized: The kidneys receive about 20% of the body’s blood per minute! B. Highly Organized 1. Aorta → Renal Artery → Segmental Arteries → Interlobar Arteries → Arcuate Arteries → Interlobular Arteries → 2. Afferent Arterioles → Glomerulus (Glomerular Capillaries) → Efferent Arterioles → Peritubular capillaries (cortical)/Vasa recta (medullary) → Venules 3. Interlobular Veins → Arcuate Veins → Interlobar Veins → Renal Vein → IVC C. The Renal Artery, Renal Vein, and Renal Pelvis all converge at the Hilum. The Nephron I. Where the CV and Urinary System Intersect! II. Two Types of Nephrons: A. Cortical Nephrons (~85%) - mostly contained within the cortex of the kidney. 1. Surrounded by Peritubular Capillaries 2. Responsible for “cleaning” the blood. B. Juxtamedullary Nephrons (~15%) - located on the cortico-medullary border, with its LoH extending deep into the renal medulla.  1. PCT and DCT surrounded by Peritubular Capillaries 2. LoH is surrounded by Vasa Recta [Capillaries] 3. Responsible for urine concentration C. **We will focus on Cortical Nephrons** III. Components A. Bowman’s Capsule/Glomerular Capsule 1. Surrounds the Glomerulus (Glomerular Capillaries) 2. Site of Filtration 3. Renal Corpuscle = Glomerular Capsule + Glomerulus B. Proximal Convoluted Tubule (PCT) C. Nephron Loop [of Henle] 1. Descending limb 2. Ascending limb D. Distal Convoluted Tubule (DCT) E. Collecting Duct (CD) - sends filtrate to the minor calyx F. Glomerulus 1. A capillary bed that sits in the Glomerular Capsule 2. Where the blood is “filtered” 3. Receives blood from the afferent arteriole. Sends oxygenated blood to the efferent arteriole. G. Peritubular Capillaries 1. A capillary bed that surrounds all other parts of the nephron. 2. Provides kidney tissues with oxygen and nutrients, and receives CO2 and wastes. 3. Reabsorbs from and secretes into the nephron. IV. Filtration, Reabsorption, Secretion, Excretion A. Filtration - one way that we “clean” our blood 1. Where plasma from the blood becomes Filtrate. 2. Filtrate - Plasma and particles that pass from the blood (Glomerulus) into the Nephron (via the Bowman’s Capsule). 3. Occurs ONLY within the Renal Corpuscle between the Glomerulus and the Glomerular Capsule 4. Filtration is passive (no extra energy needed) and non-selective. a) Factors: size of molecule and pressure behind it b) RBCs are too big to be filtered, so they do not pass through. c) Glucose, Sodium, other electrolytes (and water) are small enough to be filtered. 5. “Good” things that we want to keep are “filtered” because this is a non-selective process.  a) There are ways to “save” from the filtrate so it doesn’t get excreted. 6. Some “Bad” things are not filtered because of “chance.” There are ways to remove it from the blood besides filtration. (Secretion) 7. Glomerular Filtration Rate (GFR) - amount of blood filtered/minute by the kidney. a) If size of AA > size of EA, then GFR is higher (1) More pressure causes more plasma to be filtered. b) If size of AA < size of EA, then GFR is lower (1) Less pressure means more “wastes” will go unfiltered. (2) Question: Why is very low blood pressure dangerous? B. Reabsorption - how we get the “good” stuff back into the blood from the filtrate so it isn’t excreted. 1. This requires “energy” and oxygen! 2. Water, electrolytes, and GLUCOSE, are reabsorbed along the PCT, LoH, DCT, and even CD. 3. The “desired” molecules are reabsorbed into the Peritubular capillaries, which surround the entire nephron. C. Secretion - how we get the remaining unfiltered wastes out of the blood and into the nephron. 1. Occurs between the Peritubular capillaries and the PCT, LoH, DCT, and CD of the Nephron. 2. Requires energy and oxygen! D. Excretion - filtrate (wastes and remaining water) in the nephron leaves the CD and moves towards the minor calyx 1. The filtrate now becomes urine. Anatomy of the Ureters, Urinary Bladder, and Urethra I. Ureters A. Cavity/Position 1. Retroperitoneal Cavity 2. Descends from renal pelvis, posterior to bladder, and enters bladder inferiorly at the ureteric orifices. B. Description 1. Tubular 2. 8-12” long, 1/10” diameter C. Function - Transport Urine from the Renal Pelvis and into the Urinary Bladder.  D. They have smooth muscle that helps propel urine from the kidney and into the bladder. E. There is a valve/flap to prevent the backflow of urine from the bladder into the ureters. II. Urinary Bladder A. Cavity/Position 1. Pelvic Cavity 2. Posterior to the pubic symphysis B. Description 1. Hollow - can hold up to 800mLs of urine, but is full at 500mLs 2. Muscular - a) Detrusor Muscle - smooth muscle in the wall of the bladder. 3. Landmarks a) Fundus b) Rugae - anatomical folds for expansion of bladder c) Trigone - a smooth area on the floor of the bladder forming a triangular shape between the two ureteric orifices and the internal urethral opening. d) Neck - surrounds internal urethral sphincter 4. Function - Temporarily stores urine for elimination 5. Internal Urethral Sphincter a) Smooth Muscle b) ANS Control III. Urethra A. Cavity/Position 1. Pelvic Cavity 2. Begins at neck of urinary bladder B. Description 1. In Females: 1-1.5”, extends from neck of bladder to the vestibule (near vaginal opening) 2. In Males: 7-8”, extends from the neck of the bladder to the urinary meatus. C. Function - moves urine from the bladder to the outside D. External Urethral Sphincter 1. Skeletal Muscle 2. Somatic control. Blood Calcium Homeostasis - Revisited I. Homeostasis Components A. Regulated Variable - Blood Calcium Levels (8.5-10.2 mg/dL)  B. Sensor/Controller - Parathyroid 1. Messenger: PTH (if low levels of serum calcium are detected.) C. Effectors 1. Osteoclasts (bone resorption) 2. Intestines (increase absorption of calcium) 3. DCT of the Nephron - Increase Calcium Reabsorption from the Filtrate II. Type of Feedback - Negative Blood Pressure - ADH I. Homeostasis Components A. Sensor - Baroceptors (pressure sensors) B. Controller - Hypothalamus 1. Produces ADH and sends it to the Posterior Pituitary via the infundibulum C. Effector - DCT and Collecting Duct of the Nephron - Reabsorbs water! II. Relationship between blood volume and blood pressure A. Higher blood volume = higher blood pressure B. Lower blood volume = lower blood pressure C. Diuretic drugs (aka “water pills”) decrease blood pressure by preventing water from being reabsorbed. Thus, more water remains in the filtrate and becomes urine. III. Type of Feedback - Negative Blood Pressure - RAAS I. Complex System - See Handout