Respiration and Circulation PDF

Respiration & Circulation Definition: Diagram: Respiration is a biochemical process where organic compounds (mainly glucose) are oxidized to release energy in the form of ATP (Adenosine Triphosphate), which is used for various cellular acti...

Respiration & Circulation Definition: Diagram: Respiration is a biochemical process where organic compounds (mainly glucose) are oxidized to release energy in the form of ATP (Adenosine Triphosphate), which is used for various cellular activities. In aerobic respiration (occurring in the presence of oxygen), glucose is broken down into carbon dioxide and water, releasing energy. General Equation for Aerobic Respiration: C6H12O6+6O2→6CO2+6H2O+38ATP This process takes place inside cells, mainly in mitochondria (often called the 2. Pharynx (Throat) powerhouse of the cell). Function: A passageway for both air and food. The pharynx plays a Human Respiratory System role in speech and immune defence The human respiratory system is a network (via tonsils). of organs that ensures the exchange of Structure: gases (oxygen and carbon dioxide) o Nasopharynx (uppermost between the body and the external region): Behind the nasal environment. The key components are the cavity, allows air passage. nose, pharynx, larynx, trachea, bronchi, o Oropharynx (middle lungs, alveoli, and diaphragm. region): Behind the mouth, 1. Nose connects to the oral cavity. Function: Acts as the primary entry o Laryngopharynx point for air. It filters, moistens, and (lowermost region): Leads warms the air before it enters the to the larynx (voice box) lungs. and the oesophagus. Structure: o Tonsils: Lymphoid tissues o Nostrils: External openings that form a protective ring that allow air to enter the around the throat, guarding nasal cavity. against infection. o Nasal cavity: Internally divided into left and right 3. Larynx (Voice Box) chambers by the nasal Function: Facilitates breathing, septum. The cavity is lined protects the trachea from food with mucus and fine hairs aspiration, and produces sound (cilia) that trap dust, (speech). microbes, and other foreign Structure: particles. o Composed of cartilage plates held by muscles and membranes. o Vocal cords: Elastic, fold-like structures that vibrate to produce sound when air passes through them. o Epiglottis: A flap-like structure that covers the  glottis (opening of the o The lungs are spongy and larynx) during swallowing to elastic organs located in the prevent food from entering thoracic cavity, protected by the respiratory tract. the rib cage. o The right lung has 3 lobes, 4. Trachea (Windpipe) while the left lung has 2 Function: A tubular structure that lobes to accommodate provides a clear airway for air to space for the heart. enter and exit the lungs. o Each lung is covered by a Structure: protective pleural o The trachea is about 4-5 membrane that reduces inches long and located in friction during breathing. front of the oesophagus. Diagram: o Supported by 16-20 C- shaped cartilage rings, which provide rigidity and prevent collapse during inhalation. o Lined with mucous membranes and ciliated cells that help trap particles and expel them via coughing or sneezing. 7. Alveoli 5. Bronchi and Bronchioles Function: Alveoli are the Bronchi: The trachea divides into microscopic air sacs where the the right and left bronchi, which actual gas exchange takes place. enter each lung. Oxygen from inhaled air passes o The right bronchus is wider, through the alveolar walls into the shorter, and more vertical blood, while carbon dioxide is compared to the left expelled from the blood into the bronchus. alveoli. o Each bronchus further Structure: divides into secondary and o Thin-walled sacs tertiary bronchi, and surrounded by a network of eventually into smaller capillaries (small blood tubes called bronchioles. vessels). Bronchioles: These are smaller, o Provide a large surface area thinner branches that spread (about 70 square meters in throughout the lungs and end in adults) for gas exchange. tiny air sacs called alveoli. 8. Diaphragm 6. Lungs Function: The diaphragm is the Function: The lungs are responsible primary muscle responsible for for the exchange of oxygen and breathing. It separates the thoracic carbon dioxide with the blood. cavity (where the lungs are Structure:  located) from the abdominal Internal Respiration: cavity. Structure: A dome-shaped Oxygen Transport: muscular sheet that contracts and o 3% of oxygen is carried in flattens during inhalation, the plasma. expanding the chest cavity and o 97% of oxygen is allowing air to flow into the lungs. transported by haemoglobin (Hb), the oxygen-binding protein in red blood cells Mechanism of Respiration (RBCs). 1. Breathing (Pulmonary Ventilation) o Haemoglobin is made up of Breathing is the physical act of four Fe²⁺ ions (iron ions), inhaling and exhaling air to bring which bind to oxygen oxygen into the lungs and expel molecules. carbon dioxide. Carbon Dioxide (CO₂) Transport: Inhalation: The diaphragm o 7% of CO₂ is carried in the contracts and moves downward, plasma as carbonic acid expanding the chest cavity. This (H₂CO₃). reduces the pressure inside the o About 70% of CO₂ diffuses lungs compared to the outside, into the plasma and causing air to rush in. subsequently enters RBCs. Exhalation: The diaphragm relaxes o Inside RBCs, CO₂ combines and moves upward, compressing with water in the presence the lungs and forcing air out. of the enzyme carbonic anhydrase to form carbonic acid (H₂CO₃). 2. External Respiration Carbonic Acid Breakdown: Gas Exchange: Occurs in the o Carbonic acid is highly alveoli, where oxygen from inhaled unstable and dissociates into air diffuses into the blood, and bicarbonate ions (HCO₃⁻) carbon dioxide from the blood and hydrogen ions (H⁺): diffuses into the alveoli to be exhaled. H2CO3→CAHCO3−+H+H₂CO₃ Concentration Gradient: o Oxygen concentration in the Bicarbonate Exchange: blood: 40 mm Hg. o HCO₃⁻ ions move out of o Oxygen concentration in RBCs into the plasma, alveoli: 104 mm Hg. creating an ionic imbalance. o Carbon dioxide o To maintain the ionic concentration in the blood: balance between RBCs and 45 mm Hg. plasma, Cl⁻ ions diffuse into o Carbon dioxide the RBCs. This exchange of bicarbonate and chloride concentration in alveoli: ions is known as the 40 mm Hg. Hamburger’s The diffusion of gases is driven by Phenomenon or Chloride differences in partial pressures, ensuring Shift. efficient oxygen uptake and carbon dioxide Formation of Bicarbonates: removal. o Bicarbonates formed in the RBCs combine with K⁺ or  Na⁺ ions to form stable C6H12O6+6O2→6 compounds such as CO2+6H2O+686 kc NaHCO₃: al 2. Phosphorylation: HCO3−+Na+→NaHCO3HCO₃⁻ + Na⁺ ▪ The energy released during oxidation is Role of Reduced Haemoglobin: used to convert ADP o The hydrogen ions (H⁺) (adenosine combine with haemoglobin diphosphate) into to form reduced ATP (adenosine haemoglobin (HHb), which triphosphate) helps to maintain the pH of through the process the blood by buffering the of phosphorylation: H⁺ ions: ADP+iP+7.3 kcal→ ATP H++Hb→HHbH⁺ + Hb CO₂ Release at the Lungs: o At the lungs, due to the Hering-Breuer Reflex: partial pressure difference, the bicarbonates produced This reflex controls the depth and are broken down by rhythm of respiration. carbonic anhydrase to Respiration Control: release CO₂ and H₂O, which o Respiration is regulated by are then expelled: neurons located in the pons Remaining CO₂ Transport: and medulla of the o About 23% of the brainstem. remaining CO₂ is Inspiration Process: transported by haemoglobin o During inspiration, the lungs in RBCs as expand, stimulating stretch carbaminohaemoglobin receptors in the lungs. (HbCO₂): o These receptors send an Hb+CO2↔HbCO2Hb + inhibitory signal to the CO₂ expiratory centre, preventing further inspiration and causing the inspiratory muscles to relax. Cellular Respiration: As a result, air is expelled from the lungs during Occurs in two major steps: expiration. 1. Oxidation: ▪ Complex materials (like glucose) are broken down into Circulation: simpler compounds, releasing energy. For 1. Diffusion: example, glucose is o The net movement of oxidized to carbon particles from a region of dioxide and water, higher concentration to a releasing energy:  region of lower Blood Components: concentration. 1. Blood Plasma: Makes up 2. Types of Blood Vascular Systems: 55% of blood and is an o Open Circulation: alkaline, viscous fluid. ▪ Blood circulates 2. Blood Cells: Make up 44% through body of blood, consisting of cavities. RBCs, WBCs, and platelets. ▪ Material exchange occurs directly between blood and tissues/cells. Blood Cells: ▪ Low pressure, and no respiratory 1. Red Blood Cells (RBCs) / pigments are Erythrocytes: present. o Most abundant cells in the o Closed Circulation: blood. ▪ Blood circulates o They are biconcave, through blood enucleated cells that contain vessels. haemoglobin, giving them ▪ Material exchange their red colour. occurs through the o Life Span: RBCs live for lymph. around 120 days. ▪ High pressure, and o Formation: They are respiratory pigments produced in the bone (like haemoglobin) marrow of adults and in the are present. liver and spleen during foetal development. o Process of RBC Formation: Known as Circulation Types: erythropoiesis. o Increase in RBCs: Leads to 1. Single Circulation: polycythaemia. o Blood passes through the o Decrease in RBCs: Leads heart only once, typically to erythrocytopenia. seen in systems with venous 2. White Blood Cells (WBCs) / hearts. Leucocytes: 2. Double Circulation: o WBCs are colourless, o Blood passes through the nucleated, and amoeboid in heart twice, once in the shape. pulmonary circuit (to the o They can move out of lungs) and once in the capillary walls (a process systemic circuit (to the rest called diapedesis). of the body). o Decrease in WBC count: Leads to leucopoenia. o Temporary increase in WBC count: Leads to Composition of Human Blood: leucocytosis. o Life Span: WBCs have a Blood Volume: The average adult life span of 13 to 20 days. human has 4 to 6 Liters of blood.  complexes. They also produce anti-toxins. 2. A granulated / non-granulated Types of WBC (White These cells do not have visible granules in Blood Cells) their cytoplasm. White blood cells (WBCs) are essential Lymphocytes components of the immune system and are o Appearance: Smallest categorized into two main types based on WBCs with large nuclei. the presence or absence of granules in their o Abundance: 26-30% of cytoplasm: WBCs. o Function: Major 1. Granulated / Granulocytes components of the immune system, involved in the These cells contain visible granules in their production of T-cells and B- cytoplasm. cells. Monocytes Neutrophils o Appearance: Largest WBCs o Appearance: Large cells with a bean-shaped nucleus. with fine granules and o Abundance: 3-8% of WBCs. several lobed nuclei. o Function: Phagocytic cells o Staining: Neutral (neither that help in engulfing large acidic nor basic). foreign particles and dead o Abundance: Comprise 76% cells. of WBCs. o Function: Phagocytic in nature, meaning they engulf and digest foreign particles Platelets / Thrombocytes or microorganisms. Basophils Appearance: Small, oval-shaped o Appearance: Large cells fragments of cells without nuclei. with few granules. Formation: Produced in the bone o Staining: Basic staining. marrow. o Abundance: 0.5-1% of Lifespan: 5 to 9 days. WBCs. Function: Essential for blood o Nucleus: Twisted. clotting. o Function: Non-phagocytic; o Platelets decrease in number secrete heparin, histamine, can lead to haemorrhage. and serotonin. o Secrete serotonin, which Eosinophils constricts blood vessels to o Appearance: Lysosomal reduce blood loss. granules present; twisted nucleus. o Staining: Acidic. Blood Clotting Process o Abundance: 1-3% of WBCs. Definition: Conversion of liquid o Function: Phagocytic and responsible for destroying blood into a solid form to prevent antigens-antibody excessive bleeding.  Mechanism: Grooves: The chambers are o It involves 12 clotting separated by the transverse groove factors and two pathways: (coronary sulcus), and the ▪ Intrinsic and ventricles are separated by inter- Extrinsic pathways ventricular sulci. which lead to the Major vessels: formation of o Right ventricle: Contains thromboplastin. the pulmonary trunk. ▪ Thromboplastin o Left ventricle: Contains the inactivates heparin aorta. and activates o The pulmonary trunk and thrombin, aorta are connected by the converting ligamentum arteriosum. fibrinogen into o The aortic arch gives rise fibrin, forming to the brachiocephalic blood clots. artery, common carotid, and left subclavian artery. Atria: o Right atrium receives blood from the superior The Human Heart and inferior vena cava. o Left atrium receives blood Overview from the pulmonary veins. Function: The heart is a muscular organ responsible for pumping blood throughout the body. Location: Situated in the Internal Structure of the mediastinum (the space between Heart the lungs), with a conical shape and tilted toward the left. Chambers: The heart consists of Enclosure: Encased in a four chambers: two atria (right and membranous sac called the left) and two ventricles (right and pericardium. left). o Pericardium: Two layers – o The atria are thin-walled an outer fibrous layer and receiving chambers. an inner serous layer, o The ventricles are thick- divided into the parietal walled pumping chambers. and visceral layers, Septum: The chambers are separated by pericardial separated by the inter-auricular fluid. septum and inter-ventricular septum. External Structure of the Heart Right Atrium: Receives blood from the superior vena cava, Chambers: inferior vena cava, and coronary o Upper chambers: Atria or sinus. Auricles. o The inferior vena cava and o Lower chambers: coronary sinus have Ventricles. openings guarded by the Eustachian valve and  Thebesian valve, The heart is equipped with specialized respectively. cardiac muscle tissue, called nodal fibres, Left Atrium: Receives oxygenated which are responsible for initiating and blood from the lungs through four transmitting electrical impulses that control openings of the pulmonary veins, the heartbeat. The conduction system of the which do not have valves. heart includes the following key Valves: components: o Right atrium opens into the right ventricle through the 1. Sinoatrial (SA) Node: tricuspid valve. o Located at the base of the o Left atrium opens into the Superior Vena Cava left ventricle through the (SVC) in the right atrium. bicuspid (mitral) valve. o Known as the natural Ventricles: pacemaker of the heart, it o The right ventricle pumps generates electrical impulses blood into the pulmonary that initiate each heartbeat. artery. 2. Atrioventricular (AV) Node: o The left ventricle pumps o Found at the base of the blood into the aorta. right atrium, near the o Both ventricles are guarded interatrial septum. by semilunar valves at their o It acts as a relay station, respective openings to receiving electrical impulses prevent backflow of blood. from the SA node and passing them on to the Blood Conduction in the ventricles. 3. Bundle of His: Heart o A collection of specialized cardiac fibres that are The heart's rhythmic contraction and connected to the AV node. relaxation cycles are vital for pumping o It plays a critical role in blood throughout the body. These cycles transmitting electrical are known as: impulses from the AV node to the ventricles. Contraction (Systole): This is the 4. Purkinje Fibers: phase when the heart muscle o These fibres are an contracts, forcing blood out of the extension of the Bundle of chambers. His, spreading the electrical Relaxation (Diastole): In this impulse throughout the phase, the heart relaxes and the ventricular walls, ensuring chambers refill with blood. coordinated contraction of the ventricles. Heart Rate How the Conduction System Works The normal heart rate is approximately 72 beats per minute SA Node: under resting conditions. o The electrical impulse generated by the SA node Cardiac Conduction System starts a wave of contraction in the atria, causing them to  push blood into the ventricles. Impulse Travels to AV Node: o The impulse is then transmitted to the AV node. From here, the electrical signal travels through the Bundle of His and down to the rest of the heart. Bundle of His: o This bundle divides into right and left branches, which carry the impulse through the interventricular septum and into the walls of the right and left ventricles. Purkinje Fibers: o The network formed by the Bundle of His branches is called the Purkinje fibres. These fibres spread the electrical impulse to the ventricular walls, ensuring that both ventricles contract simultaneously and efficiently, pumping blood out of the heart (right ventricle to the lungs and left ventricle to the rest of the body). Summary of the Process 1. The SA node generates the electrical impulse. 2. The impulse spreads through the atria, causing them to contract. 3. The signal reaches the AV node, which relays the impulse to the Bundle of His. 4. The Bundle of His divides into right and left branches, sending the impulse through the ventricles. 5. The Purkinje fibres ensure the signal reaches all parts of the ventricles, leading to their contraction and the efficient ejection of blood.