The Urinary System Chapter 17/26
One of the many functions of the urinary system is to rid the body of waste materials. A human waste product is any substance that has no function, for example, excessive carbon dioxide from cellular respiration, toxic nitrogen-containing molecules from the breakdown of proteins, and uric acid from the breakdown of nucleic acids. Even excess water needs to be removed. Several tissues, organs, and processes of this organ system contribute to the temporary confinement of wastes, transport of waste materials, and excretion of wastes from the body.
Contents:1. Kidney
2. Ureter
3. Urinary Bladder
4. Urethra
Functions:
1. Remove nitrogenous wastes from blood (produces urine)
2. Storage and removal of urine from body (micturition)
3. Regulation of blood volume
4. Regulation of ions in blood (Na+)
5. Regulation of blood pH (H+)
6. Participation in Vitamin D metabolism. (converts precursor into active form)
7. Hormone secretion (endocrine organ)
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1. Kidney: general information
paired, bean-shaped organs located in superior and posterior corner of abdominal region (*not cavity).
About 4-5 inches long, 2-3 inches wide, 1 inch thick.
An adrenal gland lies at superior end of each kidney.
Right kidney slightly more inferior than left, due to presence of liver.
On medial side of each kidney is a depression (hilum or hilus pl)
Technically, kidneys lie exterior to abdominal cavity. Lie exterior to parietal peritoneum. *retroperitoneal
hormones secreted: 1. Erythropoietin – stimulates production of new blood cells
2. Renin – regulates blood pressure & kidney function
2. Kidney: external coverings- there are three layers of connective tissue surrounding each kidney:
A. Renal fascia. A thin sheet of dense regular connective tissuea. Function: anchors kidney to posterior abdominal wall
B. Adipose capsule = renal fat pad. Made of adipose tissue. a. Function: protects kidney from physical injury
C. Renal capsule A thin sheet of dense irregular Connective Tissue. Smooth layer resting directly up in kidney tissue
a. Function: protection
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3. Kidney: internal anatomy- 3 major regions:
A. Cortex a. Outer region of kidneyb. Reddish in colorc. Spectrum of cortex tissue. Extend deeper into kidneyd. Renal columns
B. Medullaa. middle region of kidneyb. consists of 8-18 shaped structures (pyramids)c. tip of each pyramid faces inwardd. tip called renal papilla
C. Sinusa. inner region of kidneyb. a space or cavity, not a physical structurec. sinus filled with adipose and renal pelvis
Renal pelvis = expanded and flared out superior end of ureter.
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Minor calyx relatively small spaces that collect drops of urine that flow out of renal papillae
Major calyx relatively large spaces that collect drops of urine from several minor calyses (2-3/kidney)
4. Renal blood vessels http://www.youtube.com/watch?v=lfGYd1wrTgE
Each minute, about 20% of all oxygenated blood leaving the heart goes to both kidneys. Highly vascularA series of decreasing diameter arteries extend deep into each kidney
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a) Renal Arteries – branches off aorta, enter renal sinus at hilum
b) Segmental arteries – up to 6/kidney. Located within renal sinus
c) Interlobar arteries – travel parallel to renal columns
d) Arcuate arteries – arch over the base of pyramid
e) interlobular arteries – small arteries that extend into cortex region
f) afferent arteriole – bring blood to a nephron
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5. Ureter
A pair of muscular tubes that carry urine from kidney to urinary bladder
Each about 10 inches long
Retroperitoneal in location
Superior end is greatly expanded (renal pelvis)
Occupies most of renal sinus in kidney
Lined with transitional epithelium
Stretches and relaxes with flow of urine
Smooth muscle in ureter wall & contracts with peristalsis
Contractions push urine toward bladder
6. Urinary bladder
A hollow muscular sac that temporarily stores urine.
Holds about 700-800 ml
*Retroperitoneal (external to the peritoneal lining of the abdominal cavity)
Lined with: transitional epithelium
Size and location varies with gendero Empty: bladder lies entirely within pelvic cavityo Full: extends superiorly into abdominal cavity to level of umbilicus
At junction with urethra, smooth muscle thickens to form a sphincter: internal urethral sphincter
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7. Urethra
A muscular tube that carries urine from bladder to external environment
Lined with stratified columnar and transitional epithelium
Has two sphincterso Internal urethral sphincter (smooth muscle)o External urethral sphincter (skeletal muscle)
a. Female
About 1-2inches long
Passes through muscular floor of pelvis
Opening to external environment located just superior to vagina
External urethral orifice
b. Male
* About 8-9 inches long
* Passes through muscular floor of pelvis
*Passes through prostate gland and entire length of penis
* Opening to external environment located at tip of penis (external urethral orifice)
Quiz #1
8. Nephron * Functional unit of the kidney*
A microscopic tube in which urine is formed
Over 1 million nephrons per kidney
Lined with simple cuboidal
2 major sections: renal corpuscle and renal tubule
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A. Glomerulus* A small tuft or tangle of capillaries located off the afferent arteriole.
B. Glomerular (=Bowman’s) capsule* A C-shaped tube that surrounds glomerulus (plasma flows into nephron here)
C. Proximal convoluted tubule* Short portion of tubule that has flexures
D. Loop of Henle* Long portion of tubule that dips down into medulla
E. Distal convoluted tubule* Second portion of tubule that has flexures
F. Collecting duct* A central tube that collects urine from many adjacent nephrons
* Empties into minor calyx at renal papilla
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9. Formation of Urine - Three major steps to produce urine
A. Glomerular filtration
Occurs at renal corpuscle (glomerulus and glomerular capsules)
Transfer of plasma (and most all dissolved or suspended materials) from glomerulus into glomerular capsule
Movement occurs without ATP because of force of blood pressure in glomerulus
Fluid (and materials)within nephron = filtrate
Filtrate contains most all common blood components except: formed elements and larger proteins
Glomerular filtration rate (GFR) = the amount of filtrate produced by both kidneys. This is approximately 125 ml/min or 180 L/day.
Summary: A large amount of plasma enters the nephron and becomes filtrate
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B. Tubular reabsorption
Occurs at proximal convoluted tubule and loop of Henle
Movement of needed materials (ex: water, nutrients, ions) from filtrate Back into interstitial fluid blood
About 99% of filtrate actually is returned back into plasma
Some materials simply diffuse, others must use active transport
Remaining 1% of filtrate forms urine.o Contains mostly water, all metabolic wastes, some unneeded ionso About 1.8 L/day produced
Summary:o Most all needed materials and water is returned to blood from filtrate o Waste products and small amount of water in filtrate now called urine.
C. Tubular secretion
Occurs in the loop of Henle and distal convoluted tubule and collecting duct.
The final transfer of nitrogen waste products from blood back into urine.
Movement occurs by active transport, forcing wastes into urine against a concentration gradient.
Hormones that regulate water ions in body influence cells here (aldosterone-salt) (ADH-water)
Summary: final transfer of excess ions and waste products, water back into urine, using ATP.
10. Micturition reflex
Release of urine from urinary bladder into external environment
o Begins with bladder filling up with urine
o Urine pushes against wall of bladder, beginning reflex
o Internal urethral sphincter relaxes
o If person is ready, voluntary relaxation of external urethral sphincter
o Urine exits body by muscular contraction of bladder wall
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11. Disorders of the urinary systemA. Urinary tract infection (UTI)
A bacterial infection of urethra and/or urinary bladder
Infection can spread into kidney, causing loss of kidney function
More common in women
Symptoms: burning /pain on micturitionFrequent micturition
Treatment: Antibiotics
B. Kidney stone
Precipitation of salts within urine into a solid mass within ureter or kidney
If large enough, can block flow of urine in renal pelvis or ureter
Symptoms: severe pain in lumbar region
Treatments: sound-wave therapy, surgery, time (stone wile it on its own)
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