Mercer County Community College s3

Mercer County Community College Science/Allied Health

Bio 104 Lecture Outline Urinary System Course Coordinator: Chapters: 24, 25

L. Falkow 3/05

I. Introduction

A. Components 1. Kidneys nephron 2. Ureters 3. Urinary bladder 4. Urethra

B. Functions 1. Regulate blood volume and BP

2. Regulate concentration of ions

3. Regulate blood pH

4. Eliminate waste products

5. Help liver in detoxification of poisons

II. The Kidneys A. Gross Anatomy 1. Location

2. Size and shape

3. Surrounding structures: a. liver, colon, duodenum

stomach, pancreas, jejunum, colon

b. fat and CT innermost: renal capsule middle: adipose capsule outermost: renal fascia

Clinical condition: floating kidney

c. adrenal glands

d. ureters

B. Sectional Anatomy 1. hilus (hilum) 2. cortex 3. medulla 4. renal pyramids 5. renal papilla 6. renal columns 7. renal pelvis 8. minor and major calyx (calyces)

C. The Nephron = renal corpuscle + renal tubule

1. Renal corpuscle a. Bowman's capsule parietal epithelium:

capsular space:

visceral epithelium: b. Glomerular capillaries

filtration membrane:

Glomerulonephritis -

2. Tubules

a. proximal convoluted tubules (pct)

function

b. loop of Henle

descending limb

ascending limb

c. distal convoluted tubules (dct)

function

d. Juxtaglomerular apparatus (JGA) = macula densa + juxtaglomerular cells EPO (hormone)

renin (enzyme) When BP is too low, JG cells secrete renin. Renin-angiotensin system is activated and angiotensin is formed which ______BP.

e. Collecting System

collecting ducts

papillary ducts

Urine collecting duct papillary duct --> minor calyx ---> major calyx ---> renal pelvis ---> ureter ---> urinary bladder ---> urethra ---> OUTSIDE the body

3. Nephrons (2 types): cortical

juxtamedullary

D. Blood Supply to the Kidneys

1. Route of blood: Renal artery -----> ______----> Interlobar arteries

---> Arcuate arteries ----> ______------> Afferent arteriole

---> Glomerulus ----> ______----> Peritubular capillaries, Vasa recta

------> Interlobular veins ------> ______------>

Interlobar veins ------> Segmental veins ---> ______

2. Distinctive features: a. 2 capillary beds

b. efferent arteriole

More resistance to flow out of the glomerulus than going into the glomerulus.

III. Renal Physiology

A. Basic Principles of Urine Formation waste products: urea

creatinine

uric acid

processes: filtration

reabsorption

secretion

B. Filtration

1. Pressures

glomerular hydrostatic press. (GHP)

capsular hydrostatic press. (CsHP)

blood colloid osmotic pressure (BCOP)

Filtration pressure (FP) = (GHP - CsHP) - BCOP

2. Glomerular Filtration Rate (GFR) = 125 ml/min ---> 180 liters/day

3. Glomerular filtrate Small molecules and ions can pass through filtration slits:

Ions Nutrients Wastes H2O Na+ glucose urea K+ a.a. creatinine Cl- ammonia

HCO3- uric acid

C. Reabsorption 1. ~ 99% of filtrate is reabsorbed

2. Only certain substances are reabsorbed:

H2O, ions, glucose, a.a.

3. Reabsorption occurs by: facilitated diffusion active transport diffusion osmosis countercurrent

Hydrostatic pressure in peritubular capillaries -

Osmotic pressure in peritubular capillaries -

===> osmotic pull is stronger and diffusion gradient is set up that is greater in

the peritubular capillaries than the hydrostatic force OUT of these capillaries.

===> much of H20, ions, a.a. are reabsorbed (returned) to the blood.

D. Countercurrent multiplication - based on arrangement of:

1. increasing concentration of salt, progressing from cortex ---> tip of medullary pyramid

2. max. conc. that can develop: ~ 1200 mOsm/l 3. fluid delivered to dct is hypotonic (~1/3 of solute conc. as the pct)

Functions: ** 1) efficient way to reabsorb water and solutes before filtrate (tubular fluid) reaches dct and collecting system

** 2) sets up a concentration gradient that allows passive reabsorption of water from tubular fluid in collecting system E. Secretion -

Ions Wastes Others K+, H+ ammonia neurotransmitters creatinine histamine some drugs

1. rids body of certain materials

2. controls blood pH by secretion of: H+ and NH4+ ---> urine pct loop of Henle dct collecting system

F. Control of Urine volume and Osmolarity

obligatory water reabsorption

facultative water reabsorption

ADH: If solute conc. is too high in blood (ex. salt): hypothalamus ---> post. pituitary ---> plasma ADH

---> increased H2O reabsorption in dct and collecting system

diabetes insipidus: deficiency of ADH

Aldosterone:

G. Vasa Recta

H. Summary of Renal Function

I. Composition of Urine

pH Specific Gravity

H2O Volume Color Odor Bacteria

IV. The Ureters, Urinary bladder, and Urethra

A. Ureters 1. Characteristics 2. Histology

3 tissue layers:

calculi =

B. Urinary bladder

1. Characteristics

trigone

2. Histology

detrusor muscle

C. Urethra

external urethral sphincter

Female Male size: 3-5 cm 18-20 cm walls: ext. sphincter: urinary & reproductive passageways: separate together

parts: single 3 parts: structure prostatic membranous penile

D. Micturition

1. micturition reflex

combination of involuntary and voluntary responses

V. Clinical Situations

Glomerulonephritis

Hemodialysis

Calculi