Davis: Urinary Tract System

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1. Gross anatomy, physiology on the urine production and excretion

Metabolites

Toxic byproducts of cellular metabolism

Urinary System

mediated by kidneys, removes toxic waste from blood while retaining essential materials in the process.

Primary Structures

1. Kidneys - 2
2. Ureters - 2
3. Bladder
4. Urethra

Functions of the Urinary System

1. Excretes waste via urine production
2. Regulation of BP, Blood Volume and bodily pH volumes
3. Regulation of electrolytes
4. Vitamin D Production
5. Regulation of Hemopoiesis

Electrolytes

- charged ions maintained for bodily functions, concentrations need to be at a certain level.
- Na⁺, K⁺, Cl⁻, Ca²⁺, PO₄²⁻

Erythropoeitin

hormone secreted by the kidney to stimulate production of RBC

Kidney's Structure

- bean shaped
- size of closed fist
- Retroperitoneal - behind the peritoneum
- posterior in the body on either side of the cerebral column

Layers of Tissue surrounding Kidneys (Superficial to Deep)

1. Renal Fascia - binds to inside abdominal wall
2. Adipose CT - shock absorber
3. Renal Capsule - Dense Fibrous CT

Hilus/Hilum

medial surface openings in kidneys where arteries, veins, nerves, and ureters enter and exit

Tissue Layers within Kidneys

1. Renal Cortex
2. Renal Medulla
3. bound together by renal columns, CT bands, that originate in cortex and extend to medulla

Renal Pyramids

1. within renal columns
2. cone shaped
3. filters blood to begin the process of producing urine
4. Tips face inward

Renal Papillae

1. tips of renal pyramids
2. passes filtrate through

Minor Calyces

1. funnel shaped channels
2. receive filtrate from renal papillae
3. 8-20 channels/kidney

Major Calyces

1. 2-3/kidney
2. receive fluid from minor calyces

Renal Sinus

1 in each kidney

Renal Pelvis

extends fluid into ureters

Nephrons

1.functional units of the kidneys
2. filter blood to produce urine

Nephrology

study of the urinary system

4 Components of the Nephrons

1. Renal Corpuscle
2. Proximal Convoluted Tubule
3. Nephronic Loop or Loop of Henle
4. Distal Convoluted Tubule

2 parts of the Renal Corpuscle

1. Bowman's Capsule
2. Glomeruli

Bowman's Capsule

CT that surrounds the nephrons also surrounds Glomeruli

Glomeruli

1. capillary bed
2. filtrate leaves the blood stream and enters the kidneys via capillary filtration

Proximal Convoluted Tubule

1. fluid is drained from Glomeruli
2. fluid passes through filtration membrane
3. pass to Loop of Henle

Loop of Henle/Nephronic Loop

1. thin walls
2. allows water and solutes diffuse through
3. Drains into Distal Convoluted Tubule

Distal Convoluted Tubule

1. place or additional concentration and filtration
2. filtrate becomes urine
3. at the end of tubule there are collecting ducts that carry urine from cortex into medulla
4. some urine will enter minor calyces, and most will enter papillary ducts that drain into the renal papillae

Steps of Urine Formation

1. Filtration
2. Tubular Reabsorption
3. Tubular Section

Filtration Process

- movement of H₂O and small solutes across filtration membrane
1. Diffusion of small molecules like glucose, Na⁺, amino acids, and water into Bowman's Capsule.
2. Cells will not pass through
3. 180 L of blood is filtered a day with less than 1% converted to urine
4. 19% of blood plasma enters and is filtered out

Glomerular Filtration Rate (GFR)

- measures kidney health
- average is 125 mL:/min

Hematuria

- presence of blood in the urine

Hematuria is indicative of ....

1. kidney damage
2. kidney stones
3. kidney cancer
4. kidney infection

Nephritis

inflammation of the kidneys due to infection

Pressure Gradient for Filtration

1. 2 Types of Pressure
2. Glomerular Capillary Pressure - 50 mm Hg
3. Capsule Pressure - 10mm Hg
4. Net flow flows out of Glomerulus and into Bowman's Capsule
5. ↑ or ↓ urine production

What factors affect Pressure in the kidneys?

1. Vasoconstriction - less flow to kidneys, ↓ filtration pressure
2. Vasodilation - more flow to kidneys, ↑ filtration pressure
3. Build up of Proteins in Bowman's Capsule causes ↑ in capsular pressure
4. is also regulated by CNS to ↑ or ↓ based on outside circumstances.
5. Urea regulates healthy pressure gradient - must not be completely filtered out of interstitial fluid

Tubular Reabsorption

1. Proximal Convoluted tubule driven by a Na⁺ and K⁺ pump
2. transfer of some water and useful solutes back to blood circulation
3. Reabsorbed substances like Na⁺, Mg²⁺, Ca²⁺, Cl⁻, and small amounts of urea and move to interstitial fluid
4. Amino acids and glucose get reabsorbed by kidney tubule cells
5. 65% of H₂O and solutes in filtrate will be reabsorbed
6. some reabsorption is done in the Loop of Henle - 2 parts

Tubular Reabsorption in Descending Loop of Henle

- more solutes are added to filtrate
- water volume ↓, 15% of H₂O is reabsobed
- filtrate becomes more concentrated

Tubular Reabsorption in Ascending Loop of Henle

1. H₂O is steady but 25% of remaining solutes are removed
2. 80% of water and 90% solutes are reabsorbed
3. Remaining filtrate will enter into Distal Convoluted Tubule
4. Additional 10% of Na⁺ and 19% water is reabsorbed

Peritubular Capillaries

1. capillary bed that surrounds the nephrons that reabsorbs water and solutes at the Loop of Henle and Distal Convoluted Tubule
2. converge onto the vasa recta

Vasa Recta

1. collecting duct that empties into the renal vein for circulation
2. ???

Tubular Secretion

1. other waste products are secreted from peritubular capillaries into the Loop of Henle
2. excess H⁺, K⁺, histamines, creatinine, and drug byproducts are added to filtrate

Kidney Circulation

1. renal arteries carries blood into the kidneys for its own circulation system (not for filtration but to fuel metabolic activities)
2. Vasa Recta also produces O₂and nutrients to kidney tissue

Hormone Regulators of Urine Production

1. Antidiuretic Hormone (ADH)
2. Aldosterone
3. Atria-natriuretic Hormone (ANH)

Antidiuretic Hormone (ADH)

1. aka vassopressin
2. hormone that helps the body retain water
3. secreted from Posterior Pituitary Gland
4. Osmoreceptors will initiate the production of ADH to
5. increase water premeability of distal convoluted tubule and collecting ducts
6. As a result water volume↓, as ADH ↓ tubule becomes less permeable, diluted urine volume increases

Osmoreceptor Cells

1. located within the Hypothalamus,
2.monitor osmolarity in the blood

Osmolarity

1. concentration of solutes to water levels in the blood
2. osmolarity ↓ - water ↓, ADH ↑
3. Osmolarity ↑, water ↑, and ADH↓

Effects of ADH in response to BP

1. more than 5% change in BP will stimulate or inhibit ADH use
2. ↓ BP, ↑ ADH secretion - to make the body retain water and more blood volume
3. ↑ BP, ↓ AHD secretion - to make the body remove water

Aldosterone

1. secreted by the adrenal glands
2. helps the body retain water
3. travels to blood in distal convoluted tubules to stimulate reabsorption of Na⁺ and Cl⁻ and thus, ↓ osmolarity of blood
3. manages blood volume by controlling Na⁺ levels

Aldosterone manages Na⁺ levels by?

1. ↑ absorption of Na⁺, ↑ water volume which ↑ blood volume and ↑ BP
2. ↓ absorption of Na⁺, ↓ water volume which ↓ blood volume and ↓ BP

How is Aldosterone made?

1. The enzyme renin is secreted and enters circulation to reacts with Angiotensin, a protein made in the liver
2. that reaction forms Angiotensin I that acts on Angiotensin Converting Enzyme to form Angiotensin II
3. which stimulates the adrenal glands to make Aldosterone

When is Renin released in response to BP?

1. BP↓ because Na⁺ levels are low, renin will release
2. BP↑, renin secretion is inhibited

Atria-natriuretic Hormone

1. secreted by rt atrium when it fill with blood
2. antagonist to Aldosterone, removes water
3. inhibits Na⁺ reabsorption, inhibits ADH secretion too
4. causes body to ↑ in urine volume
5. ↓ BP and blood volume

Ureters

1. small membranous tubes
2. lined with muscle membrane that 's lined with transitional epithelium (stretchy) and secretes mucus
3. extend from renal pelvis to urinary bladder
4. flow of urine is driven by Peristalsis
5. they enter bladder at oblique angle and empty
6. msucle of bladder wall will compress ureters to prevent backflow

Bladder

1. hollow muscular chamber
2. located in the pelvic cavity, superior to pubic symphysis
3. lined with muscle membrane that 's lined with transitional epithelium (stretchy) and secretes mucus
4. Walls contain Detrusor Muscles

Location of Bladder in men

anterior to rectum and larger in size

Location of Bladder in women

anterior to vagina, smaller in size

What is the pressure of the bladder when it is empty?

0mm Hg

At what point do you feel the urge to urinate

at about 300mL and pressure ↑ as well

What is the pressure of the bladder at 100mL?

10mm Hg

Maximum Capacity of the bladder

1000mL

Destrusor Muscles

smooth muscle that contracts to force urine into the urethra

Peristalsis

1. contractions occur from sec-minutes
2. parasympathetically stimulated

Urethra

1. membranous tube
2. inferior and anterior to end of bladder
3. lined with muscle membrane that is lined with stratified squamous epithelium and secretes mucus
4. contains an external Urethral Sphincter at the end

Men's Urethra

1. extends to the penis
2. 27cm long
3. contains an Internal Urethral Spincter

Women's Urethra

1. extends into the vestibule, anterior opening of the vagina
2. 4 cm long

External Urethral Sphincter

1. skeletal muscle sphincter in the urethral wall
2. conscious control of urine flow

Internal Urethral Spincter

1. only in men
2. smooth muscle that closes off urine during ejaculation

Why are women more prone to Urinary Tract Infections?

1. short urethra, bacteria can easily travel to the bladder
2. smaller bladder
3. less gateways to block off pathogens
4. more prone to infection with age
5. pregnancy puts pressure on urinary bladder which ↓ its capacity to hold urine

What two chemicals have antibacterial effects in cranberry juice?

1. fructose
2. pronanthocyanidin
3. must be 30% cranberry by volume

Micturition Reflex

1. activated by stretch receptors in bladder walls
2. ↑ in bladder pressure will cause stretch receptors to stimulate parasympathetic signals to spinal cord
3. Causes detrusor muscles to contract and move urine to urethra
4. irritation from infection can also stimulate micturition eventhough there is no urine in the bladder

Micturition control

1. develops around 2-3 years
2. signal is intercepted by the brain and will active muscles consciously.
3. part of social awareness

Renal Calculi

1. aka kidney stones
2. small Ca secretions in the renal pelvis
3. made from Ca3(PO₄)₂and Calcium Osalate
4. stones can be jagged or smooth, only jagged cause irritation

Symptoms of Kidney Stones

1. intense pain
2. epithelial bleeding
3. ulercations to mucus membrane that may become vulnerable to infections
4. block off the ureter will cause urine backup which ↑ pressure that can lead to kidney failure

Lithotripsy

1. using ultrasound or lader technology to break stones without surgery

Some known causes of kidney stones

1. gout
2. recurring kidney infections
3. having had renal calculi before

Normal Deterioration of the Kidneys

1. in 20's - kidneys begin to shrink
2. in 50's kidneys shrink to noticeable size and continue till death
3. in 80's, there is loss of 40% kidney function

What happens when kidneys shrink?

1. ateries and ureters become twisted, kinked, or blocked off
2. glomeruli are cut off from blood source
3. nephrons are blocked off, ↓ function, harder to concentrate urine
4. ↑ in urea and creatinine
5. ↑ risk of dehydration

What happens when you loose 40% of kidney function?

1. body's sensitivity to ADH and Aldosterone ↓
2. ↓ muscle tone
3. passes more water and not enough waste
4. ↓ vitamin D production which leads to osteoporosis, poor muscular response, ↑ risk of fractures

Additional Symptoms that can lead to ↓ in Kidney functions

1. ↑ BP
2. Atherosclerosis - hardening Blood vessels
3. Diabetes - leads to eventual renal failure

Renal Insufficiency

1. aka kidney failure
2. state in which the kidneys cannot maintain homestasis due to destruction of the nephrons
3. 2 types: acute and Chronic

Acute Renal Insufficiency

1. abrupt loss of function
2. due to thrombosis or hemorrhage
3. can be reversible

Chronic Renal Insifficiency

1. long term progressive and irreversible condition

Causes of Chronic Renal Insufficieny

1. Hypertension
2. Chronic Kidney Infections
3. Physical Trauma to kidneys
4. Pronlonged Ischemia or Hypoxia
5. Atherosclerosis
6. Heavy Metal Poisoning
7. Blockage of proteins in Renal Tubules (common in transfusions)
8. Glomeronephritis

Glomeronephritis

autimmune disease where the immune system attacks its own kidneys

Active Mechanisms of Kidneys to stay helathy

1. highly regenerative
2. in physical trauma, if glomeruli are intact, healing can still occur
3. remaining nephrons will hypertrophy to compensate
4. kidney reserve, normal function only requires use of 1/3 of 1 kidney

Symptoms with 70% loss of nephrons?

1. anemia
2. axotemia - ↑ urea
3. blood acidosis

Symptoms of Uremia

1. occurs with 90% loss of nephronic Functions
2. diarhhea
3. vomitting
4. labored breathing
5. cardiac arrhythmia
6. convulsions
7. coma
8. death within days

Hemodialysis

1. artificial filtration of blood
2. blood is filtered by a machine
3. requires treatment 3-5x a week, for 4-8 hours

Risks with Dialysis

1. ↑ risk of infections from poking on veins
2. Thrombosis - blood clot in vein
3. Internal bleeding

Continuous Ambulatory Peritoneal Dialysis (CAPD)

1. mobile dialysis machine
2. not as efficient as stationary machines

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