Title Homeostasis Notes+MCQS.pdf ✅

Homeostasis Dr. Muhammad Sohail, PhD 2 Homeostasis: KEY CONCEPTS ➢ Homeostasis is the process by which organisms maintain a stable internal environment despite changes in the external environment. ➢ It is essential for the survival of living organisms because it keeps body conditions within a range in which cells can function properly. ➢ Most susceptible components of internal environment that may affected by the fluctuations in external environment are water, solutes and temperature. ➢ Most homeostatic mechanisms work through negative feedback, where a change in a condition triggers a response that reverses the change. Excretory System ➢ Kidneys and Liver are the Primary structure for eliminating wastes. ➢ Liver supports the excretory role of kidney by detoxifying many chemical poisons and producing ammonia urea and uric acid from the nitrogen of amino acid. ➢ Urea is the principal excretory product formed by liver by urea cycle. Two ammonia and one carbon dioxide molecules are shunted into urea cycle to generate one molecule of urea. ➢ The removal of water and salts from the sweat gland is for the purpose of thermoregulation and of sebum on skin is for protection against microorganism. Therefore, in context of definition of excretion, skin may not be considered as excretory organ. ➢ It maintains homeostasis by filtering the blood, removing harmful wastes, and balancing body fluids. Excretory wastes Nitrogenous Waste Description Ammonia (NH3) ➢ Highly Toxic, because it tends to raise the pH of body fluid. ➢ Highly soluble in water and diffuse rapidly across membrane. ➢ One gram of nitrogen in the form of ammonia requires 500 ml of water to dissolve into no-toxic level. ➢ Such plenty of water can only be afforded by aquatic animals. Urea ➢ Breakdown of amino acids (protein metabolism) in liver ➢ Urea is 100,000 times less toxic than ammonia and requires 50 ml water to remove 1g urea. Uric Acid ➢ Formed by breakdown of nucleic acids (purines). ➢ Less toxic than urea and just 1ml water is required for 1g. Creatinine ➢ Formed by breakdown of creatine phosphate in muscles. Amino Acids (excess) ➢ Produced due to excess protein intake or abnormal metabolism. Human Urinary System ➢ The excretory system (Urinary system) consists of kidneys, ureter, urinary bladder and a tubular urethra. ➢ The weight of kidney account for less than 1% of the total body weight while receiving 20% of blood suppled with each cardiac beat.
Homeostasis Dr. Muhammad Sohail, PhD 3 Components of Human Urinary System Organ Number Structure Main Function Kidneys (Retroperitoneal organ) 2 Bean-shaped, radish brown organs located on either side of the vertebral column between 12th thoracic and 3rd Lumber vertebrae. Filter blood, remove nitrogenous waste, form urine Ureters 2 Narrow, 25-30 cm muscular tubes connecting kidneys to the urinary bladder Transport urine from kidneys to bladder by peristaltic movement Urinary Bladder 1 Muscular, elastic sac in the pelvic cavity Stores urine temporarily until excretion Urethra 1 Tube leading from bladder to the exterior of the body Carries urine out of the body during urination Structural Parts of Human Kidney and Their Functions Structural Part Functions Renal Fascia Outermost layer of dense connective tissues around the kidney & adrenal gland Renal Capsule or Fibrous capsule Inner to renal fascia Protects the kidney from trauma and infection Renal Sinus The renal sinus is a cavity within the kidney that houses the renal pelvis, major and minor calyces, blood vessels, nerves, and lymphatic vessels Renal Cortex Outer part, Site of blood filtration; contains glomeruli and Bowman's capsules Renal Medulla Contains renal pyramids (7-18); involved in urine concentration Renal Pyramids Transport urine from cortex to calyces via collecting ducts Minor & Major Calyces Collect urine from pyramids and drain into renal pelvis Renal Pelvis Funnel-shaped reservoir for urine before it passes into ureter NEPHRON ➢ Nephron is the structural and functional unit of the kidney. ➢ Each kidney has about 1 to 1.3 million nephrons. ➢ The nephron plays a vital role in the final stages of urine formation, concentrating the urine and maintaining the body's fluid and electrolyte balance. ➢ Nephrons also play a role in hormone regulation, such as the release of hormones that regulate blood pressure and red blood cell production