Download - physiology : Excretion
Principles of physiology
Nutrition, Digestion & Metabolism
Blood
Respiration
Excretion
Muscular system
Nervous system
Endocrine system
EXCRETION
LUNG
Excrete carbondioxide and water
The wastes of cellularrespiration
Removes
toxic substancesfrom the blood
Converts
hemoglobin fromold RBC’s to bilepigments
eliminated in thefeces
LIVER
Disposal of nitrogenous wastes
Breaks down excess
amino acids (deamination)
Amino group ammonia urea
Urea transported to the kidneys by the blood
Skin sweatglands
excretostructurof the s
URINARY SYSTEM
kidneys,
ureters,
urinary
bladder
urethra
URINARY SYSTEM
kidneys (2) are beanshaped organs ,10 cm long ,located below thediaphragm nearthe back
3 main functions:
1. Excretion(remove wastes of cellularmetabolism from the blood)
2. Regulation, homeostasis(concentrations of substances found inbody fluids,plasma,pH, blood pressure)
3. Secretion (rennin, and erythropoietin)
Kidney Structure
Kidneys consist ofmicroscopic
structures called
NEPHRONS.
A NEPHRONMade of :1- Glomerulus: a network ofcapillaries
2- Bowman’s
capsule:
cup-like structuresurrounding theglomerulus
3- Renal tubule
Proximal convolutedtubule (PCT)
longest, most coiled,simple cuboidal withbrush border
Nephron loop - Ushaped; descending +ascending limbs
Distal convoluted tubule(DCT)
cuboidal, minimalmicrovilli
Juxta-glomerular apparatus:
A group of spindle shaped cells in the mediaof afferent glomerular arterioles
-Secrete rennin ( increase renal blood flow ). -Secrete erythropoietine, a hormonal agentnecessary for production of red blood cellsby bone marrow.
-Secrete chemical factor ,regulate the outputof aldosterone.
A nephron works in 3 stages: 1- Filtrations stage: water, minerals,
salts, urea, amino acids and glucose arefiltered out of the blood
Filterate170-180L/dayresemble blood plasma (except RBCs,plasma
protein
3 forces : High glomerular capillaries pressure
High glomerular osmotic pressure
Low filterate pressure
2- Reabsorptionstage:
water, minerals,amino acids and
glucose arereabsorbed byactive transportfrom the renaltubule into thecapillaries
3- Secretion stage
Urine Formation Preview
Urine Volume
Normal volume - 1 to 2 L/day
Polyuria > 2 L/day
Oliguria < 500 mL/day
Anuria - 0 to 100 mL
DiabetesChronic polyuria
With hyperglycemia and glycosuria
diabetes mellitus I and II, insulinhyposecretion/insensitivity
gestational diabetes, 1 to 3% of pregnancies pituitary diabetes, hypersecretion of GH adrenal diabetes, hypersecretion of cortisol
With glycosuria but no hyperglycemia renal diabetes, hereditary deficiency of glucose
transporters
With no hyperglycemia or glycosuria
diabetes insipidus, ADH hyposecretion
URETERS
Tubes
carry urinefrom thekidney to thebladder
URINARY BLADDER
Stores urine
URETHRA
Tube thatcarries urinefrom thebladder to theoutside of thebody
Function - Homeostasis
Acid-Base Balance Kidneys regulate the pH, mineral ion concentration,and water composition of the blood.
By exchanging hydronium ions and hydroxyl ions,the blood plasma is maintained by the kidney at pH
7.4. Urine, becomes either acidic at pH 5 or alkaline atpH 8.
Water Balance Aldosterone
Plasma Volume ADH
Aldosterone
A steroid hormone (m alocorticoid)
It is formed in the outer-section (zona
glomerulosa) of the adrenal cortex
It diminishes the excretion of Na+ ions andtherefore water, and stimulates the excretionof K+ ions by the kidneys.
ADH (VASOPRESSIN) when the body is low on water.
kidneys conserve water
osmotic activity increase
con. urine.
→ stimulate OSMOTIC RECEPTORS in thehypothalamus
→ stimulation of posterior pituitary lobe
→ activation of VASOPRESSIN→ increase collecting ducts permeability for water
→ reabsorption →HYPERTONIC URINE
Malfunctions
Kidney Diseases: Various conditions in which thekidneys are unable to properlyexcrete nitrogenous wastes
Kidney stones: Substances crystalize out of the urinein the urinary tract or in the kidney
Some pass out in the urine on theirown
Some can be shattered with lasers orsound waves
Some are surgically removed
Dialysis - cansome times be usedto treat variouskidney diseases
Kidneytransplants