Physiology Lecture Notes 2024-2025 PDF

**Physiology Lecture Notes** **Physiology of the cell and homeostasis** - **Physiology** is the study of normal body functions. - It is the study of the normal functions of a living organism and its **component** parts including all chemical and physical processes. - **[The Cell:]** -...

**Physiology Lecture Notes** **Physiology of the cell and homeostasis** - **Physiology** is the study of normal body functions. - It is the study of the normal functions of a living organism and its **component** parts including all chemical and physical processes. - **[The Cell:]** - It is the basic unit of both structure and function. - All cells perform certain basic functions such as: 1. Getting nutrients. 2. Eliminating wastes. (التخلص من الفضلات) 3. Synthesizing cellular components. 4. Respond to changes in the surrounding environments. 5. Controlling exchange of materials and reproduce. - **[Tissues:]**  - Tissues are groups of cells of similar specializations. - Primary tissue types are: 1. Muscle: skeletal, cardiac, and smooth. 2. Nervous: transmits electrical impulses. 3. Epithelial- sheets and glands. 4. Connective: few cells dispersed (متناثر) in an extracellular matrix. - **[Organs:]** - Two or more types of tissues organized to form certain function. [Example: ] - The stomach is composed of 4 tissues: - The inside surface of the stomach is lined with epithelial tissue. - The wall of the stomach contains smooth muscle. - Nerve tissue in the stomach controls muscle contraction. - These tissues are bound together by connective tissue. - **[System:]** - Collection of organs perform related functions. - Example: - Digestive system: The mouth, stomach, and small intestine are some of the organs of the digestive system. ***[The body systems are:]*** 1. Circulatory. 2. Respiratory. 3. Skeletal. 4.Integumentary. 5. Nervous. 6.Reproductive 7. Digestive. 8.Urinary.  - Body systems maintain homeostasis (=keeping the internal environment constantالمحافظة علي البيئة الداخلية في حالة ثبات ). **Body fluids and homeostasis** **[Body fluids:]** The cell which is the smallest living unit in the body exist in a fluid from which it takes up O~2~ and nutrients and termed body fluids. Body fluids are divided into two compartments: 1\. Intracellular. 2\. Extracellular. a\. Interstitial. b\. Intravascular. In man **60%** of the body weight is water. A 70 Kg adult man has about 42 litres of water (TBW), distributed into 2 major fluids compartments: 1\. 40% (2/3) intracellular (28 L). 2\. 20% (1/3) extracellular (14 L). Extracellular fluid is further subdivided into: a\. Interstitial fluid: between the cells (tissue fluid)=(11.2 L). b\. Intravascular fluid: in vascular system (blood plasma and cells) = (2.8 L). - **You should know that:** The more fat the less the total water content. So, fat people have lower water content. The younger the greater is the water content. Man 60% Woman 55% Infants 75% Fetus 97%  - **Water Balance:** **Normal fluid intake: 2-3 L/day.** **Fluid input** =2-3 L/day: (sources of water) By drinking, From food and by oxidation of food stuffs. **Fluid output**= 2-3 L/day: Urine (1500 ml), lungs (evaporation 700 ml), sweating (100 ml), and in feaces (100 ml) ❑ **Fluid balance: Fluid intake= Fluid output.** - Within the **extracellular** fluid, the major cation is **sodium**, and the major anion is **chloride**. - Within the **intracellular** fluid the major cation is **potassium**. - These electrolytes play an important role in maintaining homeostasis. **[Homeostasis (Homeo= same Stasis= staying)]**  ❑The body cells are bathed in a fluid medium, the extracellular fluid (ECF), in which are the ions and nutrients that are needed by the cells for maintenance of cellular life. ❑Cells are capable of living, growing, and performing their special functions so long as the proper concentrations of the constituents of the ECF are available. The ECF is called internal environment of the body. It is essential to maintain constant conditions in this internal environment since normal cell function depends upon this constancy. The maintenance of static or constant conditions in the internal environment is known as homeostasis. - **Homeostasis is not unlimited.** It means that the body can resist (يقاوم) changes in the internal environment but to a variable range and time. Almost all diseases are failure of homeostasis. Body depends on homeostatic mechanisms to keep the constancy of the internal environment against changes. **Homeostatic mechanisms of the major functional systems** **Basic components of homeostatic mechanism** 1- **Receptors**= sensors or detectors. Detect changes in the environment both outside and inside the body and provide information on which the action of the controlled is based. 2- **Controllers**= control centre or integrating centre. Receives the signal information from the sensors about the change. Then the integrator compares the sensor's input and the set point, it generates the signal necessary for correction of the error. 3**- Effector organs.** Respond to signal from the centre to correct the error. - Most control systems of the body act by a process of negative feedback. In negative feedback, the response of the system is antagonistic (معاكس) to the stimulus (disturbance). Any change in the quantity from a set value initiates a response which tends to bring the quantity back to its set value. It opposes change and maintains stability (the effect is opposite to the change).  Positive feedback "Vicious circles حلقة مفرغة" Here, the response is in the same direction as the stimulus, and the result is a vicious circle. Positive feedback leads to instability and often to death because +ve feedback mechanism exaggerates any change and usually the input and output enhance each other. It represents failure of homeostatic mechanisms. However, +ve feedback can sometimes be useful e.g., uterine contractions during childbirth. **[Let's think together:]** **The smallest living unit in a body is the:** a\. Organ b\. System c\. Tissue d\. Cell **The internal environment of the body is:** a\. Intracellular fluid b\. Intercellular fluid c\. Extracellular fluid d\. blood **Almost all homeostatic mechanisms act by:** a\. Positive feedback. b\. Feed forward. c\. Negative feedback. d\. None of the above. **The main cation in the extracellular fluid is potassium** a\. True. b\. false. **The main intracellular cation is sodium.** a\. True b\. false. **The main extracellular anion is chloride.** a\. True b\. false. **All positive feedback mechanisms are vicious and lead to death.** a\. True. b\. False. **Cardiovascular Physiology** **[Functional anatomy of the heart]** - The heart is a hollow (أجوف) muscular organ surrounded by a connective tissue (النسيج الضام) sac (كيس) called the pericardium. - The pericardium protects the heart and allows its contraction with minimal friction (إحتكاك). - The wall of the heart is made of cardiac muscle, and it is divided into right and left halves, each of which consists of one atrium (أذين)and one ventricle(بطين).  The right atrium is separated (منفصلة) from the right ventricle by the tricuspid valve (الصمام ثلاثي الشرفات), while the left atrium is separated from the left ventricle by the bicuspid (or mitral) valve (الصمام الميترالى). Both valves are called the atrioventricular valves (A-V valves) In the ventricles, there are certain muscle called the papillary muscle the tendons (أوتار) of which (called chordae tendinea) are attached to the A-V valves, to prevent eversion (انقلاب) into the atria during the ventricular contraction (إنقباض). The aorta arises from the left ventricle and the aortic opening is guarded by the aortic valve. The pulmonary artery arises from the right ventricle and the pulmonary artery opening is guarded by the pulmonary valve. **What is the function of the heart valves?** It allows the blood flow in one direction only.  **[Functions of the atria and ventricles]** - The atria are the entry way to the ventricles. - The ventricles pump the blood to the whole body. - The aorta pumps oxygenated blood to the whole body. - The pulmonary veins deliver oxygenated blood to the heart from the lungs, while pulmonary artery delivers deoxygenated blood to the lungs. **[Mechanism of heart beating]** - Heart rate 60-90 beat/min average 72 beats/min in adults - The impulse originates at the sino-atrial node (found in the right atrium) causes contraction of the atria. Then the impulse reaches the atrioventricular node then the impulse passes to the ventricle through His-purkinje system causing ventricular contraction.  **[Heart Sounds]**  **[The cardiac cycle]** - The cardiac cycle consists of one systole-diastole sequence(تتابع). - It lasts about 0.8 second - During atrial systole the blood passes from the atria to the ventricle, while during ventricular systole the blood passes from the ventricle to the lung on the right side and to the whole body on the left side. - During atrial diastole the atria receives blood through the superior and inferior vena cava, while during ventricular diastole the ventricles get filled with blood coming from the atria. **[The cardiac output]** - It is the amount of blood pumped by each ventricle per minute (=5.5 L/min). - The stroke volume is the amount of blood pumped by each ventricle per beat (about 80 ml/beat). **[Factors affecting the cardiac output]** - Sympathetic stimulation increases the cardiac output while the parasympathetic stimulation decreases it. - Catecholamines and thyroxin increases the cardiac output. **[Let's think together:]** 1. **Discuss factors increasing the heart rate.** 2. **The second heart sound is caused by** a\. Flow of blood from the atrium to the ventricle. b\. Closure of the mitral and tricuspid valves. c\. Closure of the pulmonary and aortic valves. d\. Heart contraction. 3. **The left ventricle of the heart** a\. Contains deoxygenated blood. b\. Pumps the blood into the pulmonary circulation. c\. Receives blood from the right atrium. d\. Pumps the blood into the systemic circulation. **Gastrointestinal Physiology** **[Components of the Digestive system أجزاء الجهاز الهضمى]** It consists of 1-Alimentary canal القناة الهضمية (starts at the mouth and ends at the anus) 2-Accessory digestive glands الغدد الهضمية المساعدة (located outside the gastrointestinal tract, however, they empty their secretions into the tract) - salivary glands. - Liver. - Gallbladder. - exocrine pancreas. 3- Glands in the wall of the stomach and small intestine. **[General functions of the gut]** 1. Food digestion and absorption(إمتصاص). Digestion is the breakdown of complex molecules into simple ones to facilitate their absorption. Digestion needs the secretion of digestive juices and wall motility. 2. Excretion of waste products (undigested & unabsorbed food) 3. Immune function. The gut wall contains lymphoid tissue which participate in immune reactions. **[Function of digestive system is performed by 4 basic processes:]** 1. Secretion 2. Motility 3. Digestion 4. Absorption I. ***Gut secretion*** There are exocrine glands located along the wall of the gut as well as the three accessory glands (salivary glands, pancreas, and liver) that secrete digestive juices that contain water, electrolytes, mucus, and different enzymes. II. ***Gut motility*** Movement of food in the digestive tract is accomplished by smooth muscle contraction (involuntary control). [Types of Gut motility ] a-Propulsive (peristaltic) movement (حركة دافعة). Function: forward movement of food at an appropriate rate for digestion and absorption. b-Mixing (segmenting) movement (حركة خلط). Segmentation contractions are the mixing movement in the small and large intestine. Function: mixing food with the digestive juices, thus helping digestion and absorption. III. ***Digestion (الهضم)*** Digestion is accomplished by enzymes that hydrolyze (تكسير المواد الكميائية) certain bonds in the food molecule to release simple molecules. IV. ***Absorption (الإمتصاص)*** Absorption occurs in the small intestine. Undigested & unabsorbed materials are excreted to the outside by the process of DEFECATION (التبرز). **[Control of gut functions]** Gut functions are controlled by I. Neural regulation: 1-Enteric nervous system (The brain of the gut). It is a network of neurons arranged in the wall of the gut. It can regulate gut functions independent of the autonomic nervous system 2-Autonomic nerves (Extrinsic innervation): a-Sympathetic. b-Parasympathetic (vagal & sacral) Sympathetic and parasympathetic nerves regulate gut function by modulating the activity of the enteric nervous system. II. Hormonal regulation: The mucosa of the gut contains endocrine cells that secrete hormones that circulate in the blood. These hormones reach the gut and regulate its motility and secretion. **[The salivary glands]** There are three pairs of salivary glands 1. Parotid 2. Submandibular (=submaxillary) 3. Sublingual **[Functions of the salivary secretions]** 1-Digestive function: Saliva contains salivary amylase that starts digestion of starch (النشا) to di and trisaccharides as well as polysaccharides. 2-Moisten the buccal cavity: helps articulation (الكلام)(aiding speech) by facilitating the movement of the lips and tongue. Acts as a solvent (مذيب) for molecules that stimulate the taste buds. 3-Defensive function: Saliva contains antibacterial (مضاد للبكتيريا) enzymes (lyzozymes), thiocyanate ions, immunoglobulins (IgA) and lactoferrin (animals lick their wounds). 4-Keeps oral pH (درجة الحموضة) at 7 and antagonizes its change. The salivary buffers (يخفف من الحموضة) are (bicarbonate and mucin). This is important since acidity increases Ca^2+^ solubility leading to its loss from the enamel of teeth. **[Swallowing (deglutition) البلع]** - It is the mechanism by which the food is transported from the mouth, through the pharynx and esophagus to the stomach. - **Phases of deglutition:** a. The buccal phase: voluntary contraction of the muscles of the tongue that push the food backwards into the pharynx. b. The pharyngeal phase: it is an involuntary phase that starts by stimulating the specific pressure receptor in the pharynx that send impulses to the swallowing centre in the brain. c. Esophageal phase: it is an involuntary peristaltic wave that conduct food from the pharynx to the stomach. 1-Storage of food. 2-Mixingخلط : ingested food is mixed with gastric secretion and produce a thick liquid mixture called chyme. 3-Secretion of gastric juice that contains HCl and enzymes (pepsin) that begin protein digestion and the intrinsic factor (which helps absorption of Vit B~12~) 4-Gastric HCl is important because: A. Activates pepsin. B. It helps absorption of IRONالحديد & Ca⁺⁺ because it causes the pH of the chyme to be acidic which favors absorption of these minerals. C. HCl cause STERILIZATION تعقيم of the ingested food: it kills the majority of ingested microorganisms. 5-Piecemeal evacuation: evacuation تفريغ of stored food in the stomach into the small intestine at a rate suitable for proper digestion and absorption by the small intestine. **[Protective mechanisms of the stomach]** 1. Mucus protective barrier. حاجز واقي مكون من المخاط THICK ALKALINE MUCUS LAYER which prevents diffusion of gastric acid, to the epithelial surface. 2. Pepsinogen is secreted in the inactive form and activated by HCl in gastric lumen. التجويف 3. Rapid turnover of the mucosal barrier. سرعة إحلال و تبديل الحاجز المخاطى **[The Pancreas]** Pancreatic juice has IMPORTANT DIGESTIVE FUNCTION because it contains digestive enzymes for digestion of: 1. Carbohydrate (pancreatic amylase). 2. Protein (trypsin, chymotrypsin and carboxypeptidase). 3. Triglycerides (Pancreatic lipase) Pancreatic juice contains sodium bicarbonate to neutralize the acid chyme to protect the intestinal mucosa. 1. Secretin: it is secreted in response to the entry of acid into the duodenum. 2. Cholecystokinin (CCK):it is secreted in response to the entry of fat and protein into the duodenum. 1. Secretory function (Bile formation) إفراز العصارة الصفراء 2. Synthesis & secretion of bile salts. 3. Synthesis of plasma proteins. 4. Metabolic functions: a-Carbohydrate metabolism: gluconeogenesis تصنيع الجلوكوز, glycogenesis تصنيع الجليكوجين , glycogenolysis تكسير الجليكوجين. It is essential for glucose homeostasis. b-Protein metabolism. synthesis of non --essential amino acids. c-Fat metabolism: Synthesis of cholesterol, lipoproteins & phospholipids. Lipogenesis تصنيع الدهون, Oxidation of fatty acids to supply energy. 5. Synthesis of 25- hydroxy cholecalciferol. 6. Storage function: Glycogen, Vitamin A (10 months), D (3-4 months), B~12~ (12 months), Iron as ferritin, copper. Vascular Function: 7. Blood storage: 10% of total blood volume. Also, after meals, the liver accommodates blood drained by the gastrointestinal tract Blood filtration: 99% of bacteria that enter the portal blood from the intestine, small blood clots become phagocytosed by Kupffer cells that line hepatic sinusoids. Removal of old red blood cells by kupffer cells. 8. Detoxification of drugs & hormones (thyroxin, steroid).  Functions of the bile 1. Neutralization of HCl: Share in HCl neutralization in the duodenum due to its high bicarbonate content. 2. Digestive function: Bile contains bile acids & salts, which are essential for digestion and absorption of fat and fat-soluble vitamins in the small intestine. Bile salts cause ***[FAT EMULSIFICATION]*** (i.e., breakdown of big fat globules into small ones to become dissolved in water), thus increasing the surface area of fat droplets available for pancreatic lipase.  **[Functions of the small intestine]** In the small intestine, chyme delivered by the stomach is mixed with intestinal juice, pancreatic juice and bile. Functions of the small intestine: 1. Complete digestion of food. The intestinal juice contains digestive enzymes that complete digestion of carbohydrates and proteins (peptidases and disaccharidases). 2. Absorption of digested food. **[Overview of digestion in the small intestine]** 1. Carbohydrate digestion is completed by disaccharidases (maltase, lactase & sucrase) in the intestinal juice. 2. Protein digestion is completed by aminopeptidase in the intestinal juice. 3. Fat digestion is completed in the lumen of the small intestine by pancreatic lipase into fatty acids & monoglycerides. **[The large intestine]**  **[Let's think together:]** 1. **Mention two functions for the saliva** 2. **The liver is involved in the following physiological process** a. It passes the food from the small intestine to the large intestine. b. Synthesis of lymphocytes. c. Synthesis of plasma proteins. d. Formation of HCl in the stomach. 3. **The stomach secretes the following enzyme in its lumen** a. Trypsin. b. Pepsinogen. c. Chymotrypsin. d. Lipase **Renal Physiology** **[The functional unit of the kidney]** The nephron is the functional unit of the kidney **[Types of the nephron]**  **[Functions of the Kidneys]** 1- Excretory function. They are responsible for cleaning the blood by removing metabolic wastes (urea, creatinine & uric acid), excess solutes, and excess water and excreting them as urine -The kidney receives about 25% of the cardiac output despite its low O~2~ consumption. Renal blood flow is 1.2 litter per minute. -Because the body has only about 5.6 liters of blood, your blood runs through the kidneys to be cleaned about once every four minutes. 2- Homeostatic function: Regulate volume, chemical composition of blood (water, salts, acids, bases), and its pH. Volume: by regulation of body water as hypervolemia increase cardiac output and blood pressure which increase urine output and the reverse with hypovolemia Osmolarity: keeping osmolarity equal 300 osmoles/l. pH: adjustment of body pH nearly at 7.4 Retention of substances essential for body as amino acids and glucose via its reabsorption even if filtrated. 3- Endocrine function: A -- Secretion of Renin by the juxta-glomerular apparatus in response to \*Decreased blood pressure \*Low sodium in blood. Effect: increase arterial blood pressure and sodium level B- Activation of Vitamin D which is important for calcium level in the blood. C-Secretion of Erythropoietin -- stimulates RBC production from bone marrow.  4-Regulation of arterial blood pressure. short term: renin --angiotensin system Long term: increased blood pressure causes increased filtration and urine and this decrease blood pressure 5- Gluconeogenesis: occurs in kidney during fasting. The kidney able to produce glucose from lactate, glycerol, and glutamine. **[What is the effect of renal failure on the body?]** 1- R.B.Cs count ? Anemia 2- Blood calcium level? hypocalcemia due impaired vit D production 3- Bone? fragile bone 4- pH of blood? metabolic acidosis 5- Blood electrolytes? disturbances in electrolytes **[Let's think together:]** 1. **Discuss the endocrinal function of the kidney.** 2. **Compare between cortical and juxtamedullary nephron.** **The endocrine system** **[What is an endocrine gland?]** It is a ductless (بدون قناة) gland that secrets hormone directly into the bloodstream through which they reach other sites where they exert (يبذل) their action.  **[Examples for endocrine glands]** **[The pituitary gland]** Site:  **[Hypothalamic connection with pituitary gland]**  **[Function of the growth hormone]** 1. Induction of growth: Growth of almost all tissues including skeletal muscles, bones, and viscera. 2. Metabolic effect: Protein anabolic hormone, increases blood glucose level, and causes lipolysis. **[Disturbances in GH secretion]** 1. Increase in secretion before puberty (البلوغ) causes gigantism (العملقة). 2. Increase in secretion after puberty causes acromegaly. 3. Decreased secretion before puberty causes dwarfism (التقزم).  [ ] **[Thyroid gland]** Thyroid hormone is secreted from the thyroid gland after getting stimulated by thyroid stimulating hormone (TSH) from the pituitary gland.  **[Function of the thyroid hormone]** 1. Calorigenic effect as it increases heat production. 2. Increases myocardial contractility. 3. Important for development of the nervous system. 4. Helps in growth. 5. Protein catabolism. 6. Increases carbohydrate absorption from the GIT. 7. Lowers blood cholesterol. **[Disorders of the thyroid gland]** 1. Hypothyroidism in adults causes myxedema. 2. Hypothyroidism in infants causes cretinism. 3. Hyperthyroidism e.g., Graves' disease. **[Parathyroid glands]** They are 4 parathyroid glands found on the back of the thyroid gland They secret parathyroid hormone. **[Functions of the parathyroid gland]** It is the major regulating factor for calcium concentrations in the body fluids. The main function of the parathyroid hormone is to increase plasma calcium concentration. Mechanism: 1. Increase calcium mobilization from bones. 2. Increase calcium absorption from the intestine. 3. Increase calcium reabsorption in the kidney. 1. Hypoparathyroidism causes hypocalcemia. 2. Hyperparathyroidism causes hypercalcemia. **[The adrenal gland]** **[Adrenal gland hormones]** **[Function of the adrenal hormones]**  **[The pancreas]** It is composed of two types of secretory glands 1. Exocrine pancreas which secrets the digestive juice. 2. Endocrine pancreas which releases hormones. **[Functions of the pancreatic hormones]**  **[Diabetes Mellitus]** Diagram Description automatically generated **[Let's think together:]** 1. **Discuss the role of the parathyroid gland in calcium homeostasis.** 2. **The posterior pituitary gland secrets** a. Thyroid hormone b. Oxytocin c. Parathyroid hormone d. Growth hormone 3. **Thyroid hormone causes** a. Decrease metabolic levels b. Increase in growth c. Increase protein anabolism d. Causes hypercholesterolemia **The reproductive system** **[The female reproductive system]** 1. The ovaries Functions (a) production of ova (b) endocrine function e.g., estrogen, progesterone, and relaxin. 2- The accessory sex organs The vagina The uterus The 2 uterine tubes (=fallopian tubes) **[Structure of the ovaries]** It is made of cortex and medulla -The cortex contains about 300,000 ovarian follicles. -The medulla contains connective tissue, blood vessels, lymph vessels, and nerves. The ovarian functions start at puberty and stop at menopause. During the period between these 2 events only one ovum is discharged from the ovaries approximately every month. **[The sex cycles in females]** - These are regular cyclic changes that occur in the adult female reproductive system. - These changes start at puberty and continues till the menopause. - The duration of each cycle varies between women, but it is about 28 days in average. - The male reproductive system includes a group of organs that make up a man's reproductive and urinary system. These organs do the following jobs within your body: - They produce, maintain and transport sperm (the male reproductive cells) and semen (the protective fluid around sperm). - They discharge sperm into the female reproductive tract. - They produce and secrete male sex hormones. - The male has reproductive organs, or genitals, that are both inside and outside the pelvis. The male genitals include: - The testicles the duct system, which is made up of the epididymis and the vas deferens - The accessory glands, which include the seminal vesicles and prostate gland. - The penis. **[How does the male reproductive system function?]** The primary hormones involved in the functioning of the male reproductive system are follicle-stimulating hormone (FSH), luteinizing hormone (LH) and testosterone. FSH and LH are produced by the pituitary gland. It's located at the base of your brain and it's responsible for many functions in your body. FSH is necessary for sperm production (spermatogenesis). LH stimulates the production of testosterone, which is necessary to continue the process of spermatogenesis. Testosterone is also important in the development of male characteristics, including muscle mass and strength, fat distribution, bone mass and sex drive. **[Testicles (testes)]** The testes are oval organs that lie in the scrotum to keep it cool. Men have two testes. The testes are responsible for making testosterone, the primary male sex hormone, and for producing sperm. Within the testes are coiled masses of tubes called seminiferous tubules. These tubules are responsible for producing the sperm cells through a process called spermatogenesis. **[Let's think together:]** **1- Describe the physiological changes in the follicular phase of the ovarian cycle.** **2- The corpus albicans is formed during** a\. The follicular phase. b\. The ovulatory phase. c\. At the end of the luteal phase without pregnancy. d\. At the end of the luteal phase with pregnancy. **3- The testis is responsible for** a\. Secretion of FSH and LH. b\. Formation of sperms from Leydig cells. c\. Secretion of testosterone. d\. Secretion of estrogen. **Respiratory System Physiology**  **The respiratory system includes:** 1.**The respiratory airways:** They carry air between the atmosphere and the alveoli (الحويصلات الهوائية). It can be divided into: 1. Upper respiratory tract: the nose, pharynx (البلعوم), and larynx (الحنجرة). 2. Lower respiratory tract: the tracheobronchial tree. 2.**The lungs themselves:** \- The right lung has 3 lobes, whereas the left lung has 2 lobes. Each lobe is supplied by one lobar bronchus. \- **The lung tissue itself consists of:** Series of highly branched airways. The alveoli The pulmonary blood vessels. Large quantities of elastic connective tissue (elastin and collagen). **The Alveoli:** They are clusters of thin-walled, inflatable, grape-like sacs (about 300 million alveoli). ❑**Types of cells in alveoli:** \- **Type I alveolar cells**: The alveolar wall consists of a single layer of flattened epithelial cells. \- **Type II alveolar cells:** which secrete the pulmonary surfactant that facilitates lung expansion. \- **Defensive alveolar macrophages:** In the alveolar lumen. Each alveolus is encircled by a dense network of pulmonary capillaries (1000 capillary/ alveolus). \- The alveolar--capillary membrane is an extremely thin barrier (0.5 µm in thickness) thus, facilitating gas exchange. \- The total surface area of alveoli = 70 m^2^. Thus, the lungs occupy most of the thoracic (chest) cavity.  **[The pleural sac:]** A double-walled closed sac called the pleural sac separates each lung from the thoracic wall and other surrounding structures. The interior of the pleural sac is known as the pleural cavity. The surfaces of the pleura secrete a thin intra-pleural fluid, which lubricates the pleural surfaces as they slide against each other during respiratory movement. **Functions of the respiratory system:** 1\. **Gas exchange:** The primary function of respiratory system is to obtain O~2~ from atmospheric air, for use by the body cells, and to eliminate (remove) CO~2~ produced by the cells. This occurs by exchange of O~2~ and CO~2~ between the lungs and the blood. 2\. **Maintenance of acid-base balance** by altering the amount of CO~2~ expired. 3\. **Enhancement of venous return and lymph flow (respiratory** **pump).** 4\. **Metabolic and endocrine functions of the lungs.** \- Removal of certain substances from the blood e.g., serotonin, norepinephrine, and some prostaglandins. \- Secretion of angiotensin-converting enzyme (by pulmonary endothelial cells) that converts angiotensin I to angiotensin II. 5\. **Defense against inhaled foreign matter by the presence of cilia, phagocytes, and mucus secretion.** 6\. **It enables speech, singing, and other vocalization.** 7\. **The nose, a part of the respiratory system, serves as the organ of smell.** ***[Respiration]*** Respiration includes two separates, but related, processes: **a. Internal respiration:** is the intracellular metabolic processes carried out within the mitochondria, which use O~2~ to drive energy (ATP) from food, producing CO~2~ as by- product. **b. External respiration:** is the exchange of gases (O~2~ & CO~2~) between the body and external environment. ** External respiration is composed of:** **1.Ventilation:** is the exchange of air between atmosphere (external environment) and air sacs (alveoli) of the lungs. This exchange is accomplished by breathing. Ventilation is adjusted according to the body's metabolic needs for O2 uptake and CO2 removal. **2.Exchange:** gas exchange occurs between air in the alveoli and blood within pulmonary capillaries by a process of diffusion. **3.Transport:** gas transport occurs between the lungs and the tissues. **4.Diffusion:** gas diffusion between the tissue and the blood across the systemic tissue capillaries. - **The respiratory system accomplishes only steps (1) and (2), while the circulatory system carries out the remaining steps.** **Mechanics of respiration** **[Respiratory cycle is composed of:]** 1\. Inspiration: movement of the air from atmosphere to alveoli. 2\. Expiration: movement of the air from alveoli to atmosphere. 3\. Expiratory pause Respiratory rate = 12- 16 breaths/min. **[Respiratory Muscles]** Breathing is accomplished by the respiratory muscles that act to change the volume of the thoracic cavity, causing a corresponding change in lung volume. **Pulmonary Surfactant** It is a lipid surface tension-lowering agent secreted by specific secreting cells (Type II alveolar epithelium) and spreads over the surface of the water in the alveoli. **[Importance of pulmonary surfactant:]** 1\) **Lowering of the alveolar surface tension:** Thus, facilitating lung expansion and decreasing the effort needed to expand the lungs with each breath. **Surfactant deficiency:** **Respiratory distress syndrome (RDS):** a. In premature babies: Infant Respiratory distress Syndrome, IRDS. **Let's think together:** **Enumerate the functions of the respiratory system?** **Physiology of Blood** **[Introduction to Blood]** Blood is the red fluid found throughout the body and is contained in the blood vessels. The blood is the most valuable fluid in life. Blood represents about 8% of total body weight and has an average volume of 5 liters in woman and 5.5 liters in men. **Components of blood** [Blood consists of:] I. Fluid part \"plasma\" representing 55% of blood volume. II\. Cellular elements, representing 45% of blood volume. **There are three types of cells are present:** 1-Red blood cells \"Erythrocytes\" (RBC). 2-White blood cells \"Leukocytes\" (WBC). 3-Platelets \"Thrombocytes\".  **Functions of the blood** Blood maintains internal environment constant (i.e., homeostasis). [This is carried out through performing the following functions:] A**) Transport function:** 1- Blood carries O~2~ from the lungs to the tissues and CO~2~ from the tissues to the lungs to be expired (respiratory function). 2- Blood carries substances absorbed from the gastro-intestinal tract to the liver and the different tissues (nutritive function). B) **Regulation of body temperature:** Through cutaneous blood vessels and sweat glands. C) **Hemostatic function:** Blood clots when a blood vessel is cut to close the injured part and thus prevents further loss of blood from the circulating system. **D) Defensive function:** White blood cells attack organisms that invade the body. Antibodies are formed against invading organisms or foreign substances (immune mechanisms). **E) Nutritive function:** Blood provides a convenient pool of nutrients for the tissues, there are free sugars, amino acids, fatty acids, and minerals in the plasma. **RED BLOOD CELLS** **(Red Blood Corpuscles)= (Erythrocytes)** **Shape:** Non-nucleated, flat, disc-shaped cells indented in the middle on both sides (They are biconcave discs). **Number:** On average 5 million/mm3 (µL). Life span of RBC in the circulation is on the average 120 days. They are the most abundant cells in the Blood **RBCs content:** The most important constituent of RBCs is the: 1\. Hemoglobin (34%) 2\. Water (60%) **HEMOGLOBIN \[Hb\]** It is a red pigment (that is naturally colored). It appears red when combined with O~2~ and bluish when deoxygenated. **Functions of Hemoglobin:** 1\. Carriage of O~2~ from the lungs to the tissues. 2\. Helps in carriage of carbon dioxide from the tissue to the lungs (in the form of carbamino compounds). 3\. Hb is an important buffer in blood. **ANEMIA** **Definition:** It is a decrease or deficiency of RBCs number or decrease in Hb concentration or decrease in both RBCs and Hb. It can be caused either by too rapid loss or too slow production of RBCs. **Classification of anemia based on its CAUSE:** **i- [Aplastic anemia:]** Bone marrow aplasia means lack of a functioning bone marrow i.e., failure of the bone marrow to produce adequate numbers of RBCs, even though all ingredients necessary for erythropoiesis are available. E.g.: excessive X- ray exposure. **[ ii- Deficiency anemia:]** It is caused by dietary deficiency of a factor needed for erythropoiesis: (a) Iron deficiency anemia: It occurs when not enough iron is available for the synthesis of hemoglobin. (b) Vitamin B12 or Folic acid deficiency: Deficiency of either causes megaloblastic anemia (maturation failure anemia). in maturation failure anemia. **iii- Hemolytic anemia:** It is caused by rupture of excessive numbers of circulating erythrocytes i.e., excessive hemolysis). Iv- Hemorrhagic anemia: It is caused by excessive blood loss, which can be: 1- Acute e.g., bleeding from a wound. 2- Chronic e.g., excessive menstrual flow or bleeding piles. **v- Renal anemia:** In which inadequate secretion of erythropoietin hormone (as a result of kidney disease) causes insufficient red blood cell production and anemia. **Symptoms of Anemia:** Pallor. Headache. Easy fatigability. Poor concentration. Hypotension and increased heart rate. ❑**Treatment of anemia:** Treatment of the cause **[BLOOD GROUPS]**  Blood of different individuals has been classified into 4 major groups (types). These are groups A, B, AB, and O. Blood group \"AB\" is called universal recipient as it contains no antibodies to react with donor\'s blood antigens, so it can receive any blood group type. Blood group \"O\" is called universal donor as it contains no antigens to react with recipient's antibodies, so it can donate blood to any blood group type. Agglutination occurs between antigen (s) of donor\'s blood and antibodies of recipient\'s blood.  **Rh System** ❑There are many other systems. Most important is the Rh system. Those of the Rh system are of greatest clinical importance. \"D\" is the most important antigenic component. \"Rh-positive\" means that the individual has agglutinogen D. 85% of population are Rh +ve. Erythroblastosis Fetalis (Hemolytic disease of the New-born): It is a condition due to incompatibility between mother and fetus blood. It occurs due to Rh incompatibility. **Erythroblastosis Fetalis (Hemolytic disease of the New-born):** **BLOOD TRANSFUSIONنقل الدم** It is the process of transferring blood or blood-based products (as platelets or RBCs) from one person into the circulatory system of another. **Indications:** 1\. In hemorrhageنزيف from severe trauma or after surgical operation (to restore blood volume). 2\. In severe anemia (to restore Hb level). 3\. In bleeding attacks due to disturbances in clotting mechanisms or platelet function (transfusion of clotting factors). 4\. In erythroblastosis fetalis. **Dangers of Blood Transfusion:** ** I- Immediate**: a. **Incompatibility** (hemolytic) reactions as pain, jaundice and acute renal shut down. b. **Mechanical overloading** of the circulation particularly in patients with cardiac diseases. c. Transmission of diseases e.g., AIDs, and hepatitis **[Platelets]** ▪ **Definition:** The platelets are small granulated non-nucleated bodies. **Count:** The normal platelet count is 300.000 / µL (mm3 ) \[Range is 200.000 -- 500.000\]. Platelets have a major role in natural Hemostasis (the spontaneous prevention of blood loss). It is effective in stopping bleeding from small vessels. **[White Blood Cells]** **Definition:** They are the mobile units of the body\'s defense system. **Number of WBC:** It ranges from 4.000 -11.000/mm3 with average of 7.000/mm^3^. **They defend against foreign invasion in 2 different ways:** 1-**Humoral response** by secreting molecules that can eliminate the foreigner. 2-**Cellular response** by engulfing or killing the foreigner immune Cells.  **[Immune System]** **Function of the immune system:** is to protect the body against invasion by undesirable agents such as microscopic organisms, viruses, tumor cells and parasites. [The immune system can be divided into two parts:] 1. The natural (innate or non-specific) immune system. 2. The acquired (specific) immune system. The responses of the immune system are divided into two types: a) Humoral response: in which the body contains or develops a circulating element that are capable of attacking the invading organism. b) Cell mediated response: it involves cells directly eliminating the invaders. **[Let's Think Together]** 1. **Enumerate dangers of blood transfusion.** 2. **Blood represents:** a. 5% of body weight. b. 10% of body weight. c. 8% of body weight. d. 2% of body weight. 3. **One of the following is true regarding functions of the** **blood:** a. Homeostasis. b. Hemostasis. c. Defensive. d. All of the above. **Physiology of Nervous system** **[Functions of The Nervous System]** **1- Sensory:** Reception of general sensory information (touch, pressure, temperature, pain, vibration), and special sensations (taste, smell, vision, sounds). **2- Integration:** of sensory information from different parts of the body and processing them. **3- Motor:** Response generation. - **Divisions Of the Nervous system** **[The nervous system is anatomically divided into:]** **Central nervous system:** Brain and Spinal cord. **Peripheral nervous system:** Cranial nerves (12) and Spinal nerves (31). **[The nervous system is physiologically divided into:]** **Sensory nervous system:** receives different sensations from outside and inside of the body. **Motor nervous system:** which is further subdivided into: **Somatic:** controls skeletal muscles voluntary. **Autonomic**: control involuntary processes inside our body.  **[Nerves are functionally divided into:]** **The Afferent:** Carries information to the CNS about changes in the external or internal environment. **The Efferent:** Orders are transmitted from CNS via efferent fibers to the effector organs (muscles, glands) **Sensory nervous system** ❑ The sensory nervous system is a part of the nervous system responsible for processing sensory information. ❑ A sensory system consists of sensory neurons (including the sensory receptor cells), neural pathways, and parts of the brain involved in sensory perception **Motor nervous system:** The main function of the motor system in the generation of voluntary movement and sending the motor plan via descending tracts to the effector muscles. **Physiology of Autonomic nervous system**  [The Nervous system can be divided into:] **Anatomically:** the nervous system can be divided into: 1\. Central: Brain and spinal cord. 2\. Peripheral: Cranial nerves (12)- Spinal nerves (31). **Physiologically:** the nervous system can be divided into: 1\. Somatic nervous system: called voluntary nervous system: controls the activity of voluntary skeletal muscles. 2\. Autonomic nervous system: called involuntary nervous system: concerned with the unconscious control of visceral activity such as regulation of the heart, and digestive functions. **The Autonomic Nervous System** The autonomic nervous system is a part of the nervous system concerned with regulation and control of **INVOLUNTARY** processes in the body. **It controls**: - Cardiac Muscles - Smooth Muscles - Exocrine Glands **The Autonomic Nervous System** Efferent neuron: 2 efferent neuron (pre & post ganglionic) Role: Regulation (excitatory or Inhibitory) Neurotransmitter: Acetylcholine or norepinephrine. Autonomic ganglia: Present. Origin: Lateral horn cells (LHCs) of spinal cord. Center: Cerebral cortex, hypothalamus, brain stem, spinal cord. Types: Sympathetic and Parasympathetic. **Autonomic nervous system** The autonomic nervous system is a part of the nervous system concerned with regulation and control of all involuntary processes in the body. This system helps to control arterial pressure, gastrointestinal motility, and secretion, urinary bladder emptying, sweating, body temperature, and many other body activities, some of which are controlled almost completely and some only partially by the autonomic nervous system. **Divisions of the Autonomic Nervous System:** The ANS is composed of two anatomically and functionally distinct divisions: **The Sympathetic System** ** The Parasympathetic System** **Two important features of these divisions:** -**Tonic activity:** continuous mild activity all the time. -**Dual innervations:** ** Both innervate most of the organs except:** (Skin, Sweat glands, Spleen, Skeletal muscle blood vessels and Suprarenal gland (adrenal gland)), are supplied by sympathetic ONLY. The effects of the sympathetic & parasympathetic systems on the same organ usually **antagonistic** (opposite to each other) expect in salivary glands and genital organ.   **[Let's think together]** ** The nervous system is divided anatomically into somatic and** **autonomic nervous system.** ** False** ** The somatic nervous system controls involuntary processes inside the body.** ** False.** ** The center of autonomic nervous system is in the cerebral cortex** **only.** ** False.** ** The adrenal gland is a modified sympathetic ganglia.** ** True.** ** The parasympathetic nervous system predominates in stressful** **situations.** ** False.** ** The parasympathetic nervous system is anabolic system.** ** True.** **Good luck**