Fluid Compartments of the Body
Rahul's Noteblog
Notes on endocrinology
Fluid Compartments of the Body
• Body fluids are present in two main compartments inside the body.
• The two compartments are “inside” and “outside” cells.
• 2/3 is extracellular fluid, and 1/3 is intracellular fluid.
• The body is in fluid balance: water and solutes are correctly proportioned among various compartments.
• Processes such as filtration, absorption, diffusion, and osmosis provide a means to move fluid among the compartments.
• The concentrations of solutes provide the means to move water among the compartments. Water follows solute.
• Most solutes in the body are electrolytes.
• The kidneys can excrete urine of various concentrations, a very important concept as far as fluid balance is concerned.
• Some electrolytes present are: Na, K, Cl, bicarbonate, and protein.
• Water flows between compartments based on osmolarity.
• High interstitial fluid osmolarity draws water out of cells, low interstitial fluid osmolarity draws water into cells.
• Changes in osmolarity often result from changes in concentration of Na and Cl.
• Water moves such that intracellular osmolality = extracellular osmolality.
• Fluid balance between intravascular fluid and interstitial fluid is maintained by Colloid osmotic pressure balance by hydrostatic pressure in kidneys.
• Water intoxication: A state in which excessive body water causes cells to become hypotonic and to swell dangerously. This is caused by replacement of fluid loss by plain water, causing water to move into cells from ICF.
• When water loss > water gain, a condition called dehydration results.
• Dehydration is a decrease in volume and an increase in osmolarity of body fluids – stimulates thirst. Water moves out of cells into ECF causing cell shrinkage.
• Thirst center in hypothalamus: Stimulates thirst.
• Angiotensin II : Stimulates aldosterone secretion.
• Aldosterone: Increases water absorption by kidneys.
• ANP: Increases loss of water in urine.
• ADH: Decreased loss of water in urine.
What happens in cholera?
• Cholera stimulates secretion of NaCl and water.
• 5-10 liters of diarrhea per day.
• Toxin stimulates NaCl secretion by epithelial cells in Crypts of Lieberkuhn.
• ECF water loss. Acidosis, dehydration, hypovolemia, coma, circulatory failure, death.
More Notes:
• Colon: main function is to convert liquid ileal to solid feces.
• Diarrhea: an increase in frequency, volume, and fluid content of feces caused by increased motility of and decreased absorption of the intestines.
• Frequent diarrhea causes: electrolyte imbalance and dehydration.
Additional Reading:
Basic Endocrinology
Introduction to Endocrinology
1. Hypothalamic-pituitary system
2. Adrenal Hormones
3. Antidiuretic Hormone (ADH) and ECF Regulation
4. Endocrine Pancreas
5. Growth Hormone
6. Adrenal Medulla
7. Hormonal Control of Calcium and Phosphate
8. Thyroid Hormones
9. Hormones of Male Reproduction
10. Hormones of Female Reproduction
11. Fluid Compartments of the Body
12. Notes on Hypothalamus Anterior Pituitary and Thyroid
13. Additional Notes on Female Reproduction
14. Hormonal Signaling Pathways
Related Topics
1. Histology of the Endocrine System
2. Histology of the Male Reproductive System
3. Histology of the Female Reproductive System
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