Lec.11(1) - Basic Sciences PDF

Dr. Ahmed Deghidy PhD Molecular Biology Alex U, Alexandria, Egypt Field of Basic Sciences ‫الدولية‬ ‫جامعة العلمين‬ 1  Homeostasis Maintenance of steady internal conditions despite fluctuations in...

Dr. Ahmed Deghidy PhD Molecular Biology Alex U, Alexandria, Egypt Field of Basic Sciences ‫الدولية‬ ‫جامعة العلمين‬ 1  Homeostasis Maintenance of steady internal conditions despite fluctuations in the external environment. Examples of homeostasis: 1-Thermoregulation: the maintenance of internal temperature within narrow limits 2- Osmoregulation: the control of the gain and loss of water and solutes 3- Excretion: means the separation and elimination the waste materials resulting from the metabolism of ingested food, and the breakdown of tissues.  Excretion Carbohydrates and fats produces CO2 + H2O as end products proteins produces nitrogen containing end products. These excretory products are returned to the environment through:- The lungs : passes CO2 & H2O. Skin : passes water & small amounts of soluble matter. kidneys : passes water, soluble salts & nitrogenous end products. Water: Taken from external sources or may be metabolic water. Eliminated in urine, expired air and sweat. Carbon dioxide: Produced during metabolism. Eliminated mainly in expired air and partly in combination with ammonia as urea. Nitrogenous compounds: Comes from 2 sources: 1- Endogenous: From the breakdown of tissues. excreted as creatinine. 2- Exogenous: From ingested amino acids after the process of oxidative deamination. Eliminated as urea, uric acid or ammonia  Anatomy of urinary system Includes two kidneys, two ureters, the urinary bladder, two sphincter muscles, and the urethra  Morphology of the kidney renal artery enters renal vein and ureter leave Kidney is composed of outer cortex and inner medulla.  Functions of the kidney 1- Excretion of metabolic waste products and foreign chemicals 2- Regulation of water and electrolyte balances 3- Regulation of arterial pressure 4- Regulation of acid-base balance 5- Secretion, metabolism, and excretion of 2 hormones: 1- Renin 2- Erythropoietin Renin leads to the secretion of when the blood doesn't have the Aldosterone hormone which is released capacity to carry oxygen. from the adrenal cortex. Aldosterone promotes the kidneys to reabsorb the sodium (Na+) ions. Structure of the kidney The basic functional unit of the kidney is the nephron.  Nephron Basic structural and functional unit of the kidney. Its function is to: 1- regulate the concentration of water and soluble substances like sodium salts by filtering the blood 2- reabsorbing what is needed and excreting the rest as urine. Each nephron is composed of: 1- Renal corpuscle 2- Renal tubule Glomerulus: a capillary tuft that Proximal convoluted tubule receives its blood supply from an afferent arteriole of the renal Loop of Henle (U-shaped) circulation Distal convoluted tubule Bowman's capsule: surrounds the glomerulus “simple squamous epithelium”. Mechanism of urine formation: Urine is originally formed from the blood plasma. Constituent Plasma Urine Water 90-93 95 Glucose 0.08-0.12 - Proteins 7-9 - Urea 0.03 2 Uric acid 0.002 0.05 Creatinine 0.001 0.1 Ammonia 0.0001 0.04 Sodium 0.32 0.35  Urine Formation 1- The glomerular function “filtration” Due to high pressure in the glomerulus filtration of fluid from the plasma will occur (except for plasma proteins) The fluid is called filtrate. 2- The tubular function The filtrate passes through the tubules, its composition is changed due to 1- A process of Reabsorption 2- A process of Secretion About 90% of H2O is reabsorbed by the The cells of the tubules has the ability to tubular cells, in addition to the complete secrete urea, excess H+ and any other absorption of useful materials such as harmful substances (drugs). glucose and amino acids. In certain kidney diseases, this power decreases causing the accumulation of urea in blood , a case which is known as uremia.  Glomerular filtration rate (GFR) ❑ The process of filtration of the blood in the Bowman's capsule is ultra- filtration (or glomerular filtration), and the normal rate of filtration is 125 ml/min. ❑ Measuring the glomerular filtration rate (GFR) is a diagnostic test of kidney function. ❑ A decreased GFR may be a sign of renal failure. ❑ Conditions that can effect GFR include: arterial pressure afferent arteriole constriction efferent arteriole constriction Dialysis: compensating for kidney failure  Antidiuretic hormone (ADH) ❑ Hormone secreted from the pituitary gland. ❑ Important for conserving body water by regulating the absorption in the kidney tubules thus reduces the loss of water in urine. ❑ If the pituitary gland is injured leading to a deficiency in the ADH, the patient will excrete 30-40 liters of urine daily causing excessive thirst.