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Animal Nutrition, Feeds and Feeding > AAP Urinary System 2 > Flashcards

AAP Urinary System 2 Flashcards

1
Q

What are the main functions of kidneys?

A
  • excretion of wastes and toxins
  • regulation of extracellular fluid volume to ensure an adequate blood supply to vital organs
  • regulation of osmolarity
  • regulation of ion concentrations (pH)
  • production of hormones (Erythropoietin, EPO, –> stimulates bone marrow for RBC production
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2
Q

What are the three main steps of urine formation?

A
  • glomerular filtration
  • tubular reabsorption
  • tubular secretion
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3
Q

What happens during urine formation?

A
  • the kidneys filter unwanted substances from the blood and produce urine to excrete them
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4
Q

How is glomerular filtrate formed?

A

high blood pressure in the glomerular capillaries forces some plasma out of the capillaries and into the capsular space of Bowman’s capsule

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5
Q

Describe the structure of the glomerular capillaries.

A
  • contain many large openings, known as fenestrations, in the capillary endothelium
  • fenestrations are not large enough to allow blood cells or large proteins to pass through
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6
Q

Describe glomerular filtration.

A
  • glomerular capillaries contain many large openings, known as fenestrations, in the capillary endothelium
  • fenestrations are not large enough to allow blood cells or large proteins to pass through
  • it facilitates more fluid to leave the bloodstream
  • glomerular filtrate is similar to plasma except that it contains no proteins
  • the speed of filtration is determined by the glomerular filtration rate (GFR)
  • high blood pressure in the glomerular capillaries forces some plasma out of the capillaries and into the capsular space of the Bowman’s capsule, and becomes glomerular filtrate.
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7
Q

What is the purpose of kidney reabsorption?

A
  • ensures the body gets back the small useful molecules from the filtrate (in the tubule)
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8
Q

What happens during kidney reabsorption?

A
  • substances to be reabsorbed pass through the tubular lumen
  • and enter interstitial fluid (in tissue space –> interstitial space)
  • and then pass through tubular wall and capillary wall into the blood circulation
  • this is achieved by either passive diffusion and/or active transport
  • 65% of reabsorption takes place in the PCT, the remaining reabsoption takes place in the DCT and LOH
  • 80% of water, sodium, chloride, and bicarbonate is reabsorbed
  • 100% of the glucose and amino acids are reabsorbed
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9
Q

Sodium reabsorption

A
  • sodium can be reabsorbed by active transport, where transporter protein carry sodium through epithelial cell in the PCT
  • sodium ions are also reabsorbed in the LOH and DCT (as exchange for hydrogen, ammonium, or potassium ions)
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10
Q

Glucose and amino acid reabsorption

A
  • glucose and amino acids are transported and absorbed by similar process as sodium in the PTC
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11
Q

Potassium and calcium reabsorption

A
  • takes place mainly in the PCT
  • most of the potassium and calcium are reabsorbed by passive diffusion
  • reabsorption of calcium is modulated by vitamin D, parathyroid hormone (PTH) and calcitonin (by thyroid)
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12
Q

Chloride reabsorption

A
  • chloride diffuses through in response to electrical imbalance created by absorption of (Na+)
  • chloride moves by following the movement of sodium
  • water is absorbed by following osmosis once sodium, glucose, amino acids and chloride have left the tubular filtrate, water molecules follows
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13
Q

What is secretion?

A
  • the process by which the substances move into tubules (urine) from blood capillaries
  • many substances that are not filtered from blood are eliminated by this process
    (such as extra amt of hydrogen, potassium, ammonia, urea, certain drugs and other wastes)
  • occurs in PCT, LOH, DCT
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14
Q

What hormones control the urine volume regulation?

A
  • antidiuretic hormone (ADH) from pituitary gland

- aldosterone from adrenal cortex

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15
Q

What do ADH and aldosterone do?

A
  • ADH acts on the DCT (and CT) to promote water reabsorption back into blood
  • aldosterone acts on the DCT to increase reabsorption of sodium
  • causes osmotic imbalance that encourages water to follow sodium back into the blood
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16
Q

What is renin?

A
  • hormone secreted in the glomerulus in response to low arterial pressure
  • converts angiotensinogen (serum protein produced in the liver) to angiotensin
17
Q

What does angiotensin do?

A
  • causes vasoconstriction and stimulates the release of aldosterone (from adrenal cortex of the kidney
18
Q

Process to increase sodium reabsorption at DCT.

A
  • renin is secreted in the glomerulus in response to low arterial pressure
  • renin converts angiotensinogen to angiotensin
  • angiotensin causes vasoconstriction and stimulates the release of aldosterone
  • the release of aldosterone from the adrenal cortex leads to an increase in sodium reabsorption at DCT
19
Q

What are baroreceptors?

A
  • pressure sensors in the blood vessels
  • sense the change of blood pressure and relay the information to the brain to modulate blood pressure (by changing cardiac output and vascular smooth muscle)
20
Q

What are osmoreceptors?

A
  • found in the hypothalamus
  • sense the change of the blood osmotic pressure
  • modulate the secretion of ADH
21
Q

Diabetes insipidus

A
  • insufficient production of ADH by pituitary gland results in reduced water absorption by the kidney and consequently a large volume of diluted urine
  • frequent urination (polyuria)
  • frequent drinking of water (polydipsia) due to thirst
22
Q

Diabetes mellitus

A
  • commonly known as diabetes
  • due to the increased blood glucose level from insufficient insulin
  • similar symptoms as diabetes insipidus (polyuria and polydipsia)
23
Q

Structure of ureters

A
  • outer fibrous layer
  • middle smooth muscle layer
  • inner layer lined with transitional epithelium
24
Q

How does the structure of ureters help with its function?

A
  • transitional epithelium allows ureters to stretch as urine passes through
  • middle smooth muscle layer propels urine through the ureters by peristaltic contractions
25
Q

Ureters to urinary bladder

A
  • ureters enter the urinary bladder at an oblique angle
  • forms a functional valve to prevent backflow into ureter
  • when the bladder is full, urine presses the entrance to close it
    When the bladder is empty, the entrance is open to receive the urine from the ureter
26
Q

Structure of urinary bladder

A
  • lined with transitional epithelium that stretches as the bladder is filled with urine
  • the wall of the urinary bladder contains smooth muscle (known as detrusor muscle)
  • around the neck of the urinary bladder are circular muscles (sphincter muscles)
27
Q

Sphincter muscles (internal and external sphincter muscles)

A
  • internal sphincter muscle: smooth muscle under involuntary control
  • external sphincter muscle: skeletal muscle under voluntary control –> allows voluntary control of urination
28
Q

Urethra

A
  • continuation of the neck of the urinary bladder
  • carries urine from the bladder to the external environment
  • lined with transitional epithelium which allows it to expand
  • the female urethra is shorter and straighter compared to the long, curved urethra in male
  • in the female, the urethra opens on the ventral portion of the vestibule of the vulva –> only serves as urinary function
  • in the male, the urethra runs down the centre of the penis and also functions to carry semen
29
Q

Control of urination process

A
  • urination is the excretion of urine from the urinary bladder into the urethra
  • building up pressure in bladder activates stretch receptors (pressure sensor) in bladder wall
  • which activates a spinal reflex that cause bladder smoother muscles to contract
  • contraction give sensation of having to urinate
  • voluntary control of the external sphincter around the neck of the bladder allows the temporary control of urination
  • house-trained animals can exercise voluntary control of the external sphincter muscle to temporarily hold the urine
  • beyond a certain pressure limit, the sphincter eventually relaxes to release the urine

Animal Nutrition, Feeds and Feeding (19 decks)

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