Human Physiology PDF

❖ Human Physiology: study of functions of organs & systems and their integration and control Total body water "TBW" = 60% total body weight: F infants (75%) females & obese (50%) due to higher content of fat compartments: 300 moll in ECF...

❖ Human Physiology: study of functions of organs & systems and their integration and control Total body water "TBW" = 60% total body weight: F infants (75%) females & obese (50%) due to higher content of fat compartments: 300 moll in ECF - Intracellular fluid Extracellular fluid"ECF" "ICF" 2/3 = 40% 1/3 = 20% subdivions Intra vascular fluid (plasma) "IVF" 5% interstitial fluid "ISF" 15% Main K & Mg Na & Ca cation Main anion Phosphate & Cl & HCO3 d proteins bicarbonate ❖ Determination of volumes of water "Fick's principle": ↑ method: 1) amount of indicator is injected intravenously. (inert, not toxic, not utilized). 2) sample of blood is withdrawn and indicator conc. is determined. 𝑨𝒎𝒐𝒖𝒏𝒕 𝒊𝒏𝒋𝒆𝒄𝒕𝒆𝒅 Vol. of compartment (vol. of distribution)= 𝒄𝒐𝒏𝒄. 𝒊𝒏 𝒑𝒍𝒂𝒔𝒎𝒂 Application: 1. TBW: with heavy water or antipyrin. 2. ECF: inulin or Na thiocyanate. 3. Plasma vol: Evan's blue dye or plasma proteins labeled with radioactive iodine 4. ICF = TBW – ECF 5. ISF = ECF – Plasma vol. A.F. 2024 1  Homeostastis: Keeping conditions in internal environment (ISF surrounding cells) constant. Importance: essential for life: Life is compatible within limited changes in ISF → constituents (O2, CO2, glucose, different ions ………..) must be kept constant N.B.: failure to achieve homeostasis → disease → death Includes 2 exchanges: 1. Through cell membrane: between cells & ISF 2. Through capillary membrane: Between ISF & blood maintained by control systems. Components: Stimulus = change → Receptor (detect stimulus) → Control center → Effector organ(s). Feedback mechanisms: Negative feedback Positive feedback Almost all control mechanisms. stimulus progressively increases change the variable back to its response. original state or “ideal value”. Importance: accelerating processes must be completed rapidly e.g. Blood clotting & Uterine contractions during childbirth Wert plt heat loss A.F. 2024 2  BLOOD part of extracellular fluid (connective tissue in fluid state) volume: 5L in male 4.5 L in female (8% of body weight) Functions: 1. Transport (main): carries substances as O2, CO2, glucose ……. 2. Defensive: WBCs defend against micro-organisms and tumors 3. Hemostatic: Substances in blood act to stop bleeding 4. Homeostatic: continuous transport and heat distribution transport of gases PH: slightly alkaline 7.4 Composition: 1. Plasma (55%): fluid. 2. Cells (45%): RBCs, WBCs and platelets. A.F. 2024 3  PLASMA yellow clear fluid = 3.5 L (5% of body weight). clots on standing (remnant is serum = plasma – clotting factors). Composition: 1. Water: 90% 2. Organic substances: 9.1% Plasma proteins Lipids: as cholesterol, triglycerides, fatty acids and others Others: glucose, amino acids, vitamins, enzymes and waste products. 3. Inorganic constituents: 0.9% chief cation: Na+: chief anions: Cl & HCO3 [Others: phosphates and sulfates]. 4. Blood gases: O2, CO2 and N2. Plasma Proteins: (7.2-7.4 gm/dL): Sites of Formation: 1. Liver: Albumin, fibrinogen, prothrombin and 50% Globulins (α&β) 2. plasma cells of lymphoid tissues: 50% Globulins (gamma) Albumin/Globulin Ratio (A/G): Normally: 1.2-1.6 decreases in: 1. Liver diseases (liver cirrhosis and infective hepatitis): ↓ albumin production ↓ 2. Kidney diseases(nephrosis): albumin with its small size is lost in urine. 3. Infections: ↑ immunoglobulins (gamma globulins) A Functions of Plasma Proteins: 1. Osmotic Function: / total osmotic pressure of plasma is 290mmol/L= 5000mmHg: A Albumin “colloidal pressure” or “oncotic pressure” “crystalloid pressure” - & 25- 28 mmHg jj remaining by plasma proteins crystalloids Na+, Cl-, HCO3- weaker but more important (effective): - Plasma proteins cannot diffuse through capillary membrane (big MW): kept inside blood vessels regulates fluid exchange across capillary A.F. 2024 4  Albumin is the most important because: 1) greatest concentration 2) smallest molecular weight N.B.: osmotic pressure depends on conc. (number) not size of substance plasma viscosity ↑ 2. Blood clotting: Prothrombin and fibrinogen and others. coagulent 3. Viscosity: - blood is 3 times as viscous as water - plasma is 1.5 times as viscous as water. - Importance: Viscosity is important in CVS: maintaining normal ABP. - determined by: 1) RBCs: ↓ in anaemia ↑ in polycythemia 2) plasma proteins: Fibrinogen most due to: a. large molecular size blood clothing b. elongated shape. factor 4. Transport function: - Albumin and globulins ( and ) act as carriers for substances, e.g., hormones& minerals. X B U produced - Benefits: , , in liver 1) prevent their loss in urine 2) provide a reservoir in cases of increased need 5. Defensive function: -globulins (antibodies= humoral immunity) defend against microorganisms Si 6. Capillary function: - partially block pores of capillary membrane decreasing permeability. 7. Buffer function: 15% of buffering power of blood maintain pH of blood at 7.4 in spite of addition of acids or alkalis buffer system consists of weak acid and a strong base: proteinic acid and Na proteinate In normal pH of blood (slightly alkaline: 7.4): Plasma proteins are negatively charged and act as weak acids (anions) 8.Source of amino acids for tissues: for rapid replacement of tissue protein in case depleted A.F. 2024 5  Red blood corpuscles (RBCs) = Erythrocytes Structure: no nuclei (corpuscle = not true cells) no ribosomes or mitochondria Contains: K, hemoglobin and carbonic anhydrase enzyme for CO2 transport surface Hematocrite value = packed cell volume (PCV): more a re a more flexibility % ratio of RBCs to total blood volume: minimaltension onmembrane male female ↑ ↓ RBCs Count 5 million/mm3 4.5 new born, athletes old age million/mm3 and at high altitudes PCV 46% 42% Hb content 15-16 g/dL 13-14 g/dL newborns: 19 g/dl. (relative intrauterine hypoxia) Hemoglobin (Hb): red oxygen-carrying pigment of RBCs 34 % of OBC Hb content: amount of hemoglobin in 100 ml (dl) of blood: ❖ Structure: 4 subunits: gaysheel 0 2+ - Heme: protoporphyrin ring with ferrous iron (Fe ) (4 atoms in each Hb) - Globin: 4 polypeptide chains: alfa, beta , gama and delta hatsheel CO2 > - ❖ Types: polypeptide chains presence Adult hemoglobin A1 2 alpha and 2 beta 96 to 98% in adult Adult Hemoglobin A2 2 alpha and 2 delta 2-4% of Hb in adults Fetal hemoglobin HbF 2 alpha and 2 gamma in fetus N.B.: HbF has more affinity to O2 than HbA allowing extraction of O2 from blood of mother. After birth: HbF is changed to HbA (completed by 4 months). A.F. 2024 6 ❖ Chemical Reactions of Hemoglobin: with form attaches to 1. oxygen oxyhemoglobin iron loosely → (oxygenation not remains Fe2+ oxidation) ferröne 2. CO2 carbaminohemoglobin amino groups of polypeptide chains 3. carbon carboxyhemoglobin iron prevents hemoglobin monoxide carrying O2 : affinity (CO) of hemoglobin for CO is 200 times more 4.With strong oxidizing agents: ? wamm ferric not ferous - change Fe2+ to ferric iron & - hemoglobin becomes dark met-hemoglobin: cannot carry O2. - Small amounts normally formed but reduced back by met-hemoglobin reductase deficiency - Congenital - absence of enzyme leads to “hereditary met-hemoglobinema”.. Ab ic red Metl- > He Functions of RBC’s: reducese A. Functions of Hemoglobin 1. O2 transport: from lungs to tissues. 2. CO2 transport: from tissues to lungs 3. Buffering: Being a protein (six times that of plasma proteins): amount of Hb is 16 gm/dL while plasma proteins is 7.3 gm/dL. B. Function of membrane: 1. Plastic biconcave shape , advantages: a) larger surface area. b) increases flexibility: RBCs squeezed in capillaries without rupture. c) Minimal increase in tension when volume of RBCs increase in venous blood 2. keeps hemoglobin inside cell: if hemoglobin is free in plasma: 70mmtg 28 - a) renal failure: block renal tubules a b) increase work on heart: increase viscosity & colloidal osmotic pressure A.F. 2024 7  Life Span and Fate of Erythrocytes: 120 days - activity of glycolytic and other enzymes declines. - cells fragile and rupture during passage through capillaries especially spleen. - released hemoglobin is picked by macrophage system and broken into: 1) goblin: recycled in liver. 2) heme ring is opened: a. iron → bone marrow for building new RBC’s b. protoporphyrin → "bilirubin" secreted by liver in bile. - N.B.: hemolytic anemia = ↑ destruction of RBC’s: large amounts of bilirubin → yellow coloration of skin and mucous membranes “hemolytic jaundice”. Role of spleen: 1.site of erythropoeisis during fetal life 2.stores blood: add blood into circulation in acute hemorrhage 3.stores platelets 4.blood filter that removes aged or abnormal RBCs 5.in immune system: contains immune cells like lymphocytes and macrophages o Hypersplenism: spleen over functions (↑ destruction of blood cells). o Splenectomy: increased risk of infections, increased RBCs and platelet ↑ no more filtration A.F. 2024 8  Erythropoiesis: formation of erythrocytes. Sites o Fetus: liver and spleen. o After birth: bone marrow (all bones) o After 20 y: bone marrow of membranous bones (vertebrae, skull, ribs, pelvis) N.B.: - marrow of long bones becomes inactive except upper humerus and femur. - Bone marrow is one of largest and most active organs (as liver) Factors affecting Erythropoiesis: I. Oxygen supply to tissues “Role of Erythropoietin”: - "hypoxia" increases rate of production of erythrocytes as in: 1) Heart failure: decreased blood flow. 2) Lung diseases 3) Hemorrhage: loss of RBCs. 4) High altitude: decreased O2 tension in air. 5) Athletes: relative oxygen deficiency (higher oxygen requirements) Mechanism: hypoxia stimulates release of erythropoietin ❖ Erythropoietin hormone: half life of 5 hours. - Sources: fetus: liver. In adults: ▪ 85% kidneys (renal failure causes anemia) ▪ 15% liver: tissue macrophage = Kupffer cells. A.F. 2024 9  - action: combines with receptors on stem cells stimulating steps of erythropoiesis N.B.: Erythropoietin synthesized for in anemia due to renal failure. − Stimulation of Secretion: 1. Hypoxia (main stimulus): PO2 in kidney is the major factor. 2. androgens. f 3. B-adrenergic stimulants. 4. Cobalt 5. Alkalosis at high altitudes 6. Adenosine: adenosine antagonists as theophylline inhibit Erythropoietin. II. Hormones: 1) Erythropoietin specific Zuon specific 2) Androgens 3) thyroid hormones 4) glucocorticoids (cortisol) III. Healthy Liver 1) 15% of erythropoietin. 2) Storage of iron and vitamin B12. 3) Synthesis of globin IV. Healthy Bone Marrow aplastic anemia = Destruction of bone marrow = decreased all blood cells. Causes: 1) radiation: X-ray, atomic 2) drugs as chloramphenicol 3) malignant tumours. V. Diet: A. Proteins: high biological value: to build globin B. Trace Elements Copper and cobalt: cofactors for Hb formation. Cobalt: part of vitamin B12 & stimulator of erythropoietin secretion. A.F. 2024 10