CIRCULATORY SYSTEM

1. CIRCULATORY SYSTEM Two major portions : the blood vascular system and the lymphatic system. I. Blood Vascular System Serves to transport food, water, gases, hormones and waste materials in the body, defends the body, keeps the organs moist and equalizes the temperature. The fluid tissue, blood circulates in blood vessels with help of the muscular pump, the heart.

2. Heart • Appearance and position – conical, muscular organ, occupying part of mediastinum (space between two pleural sacs that enclose the lungs). • Pericardium – enclosed in a two layered sac, pericardium. Inner layer (visceral pericardium), outer layer (parietal pericardium). Pericardial cavity – space between the two layers – contains a watery coelomic fluid, the pericardial fluid. • External structure – Auriculo – ventricular groove, Interventricular groove, Interventricular groove. Auricular appendix. • Internal structure – two halves : right and left. Each half – two chambers : auricle and ventricle. Heart of rat – four-chambered. Auriculo-ventricular aperture. Musculi pectinati (network of low ridges).

3. Two auricles separated by : interauricular septum (has small oval depression – fossa ovalis). Inner surface of ventricles – network of low ridges (columnae carneae) and musculi papillares. Two ventricles separated by – interventricular septum. Right auricle – three large vessels – right and left precavals and the postcaval. Valve of Eustachius recieves coronary sinus. Valve of Thebisius. Right auriculo-ventricular aperture – guarded by tricuspid valve. Left auricle – two blood vessels : right and left pulmonary veins. Left auriculo-ventricular aperture. Left ventricle gives – aortic arch.

4. (e) Histological structure – heart – a modified blood vessel. Endocardium and myocardium. Straited fibres – have thick cross bands – intercalated discs. (f) Working – systole and diastole. Longitudinal section of the heart of rat Mechanism of heart beat

5. (g) Circulation – aerated and non-aerated blood remain reparate. Blood passes- first through right, then left (double circulation). Pulmonary circulation (right ventricle to left auricle via lungs). Systemic circulation (left ventricle to right ventricle via body). (h) Efficiency (i) Control of heart beat Blood vessels Two types : arteries and veins.

6. The arterial system of rat

7. 1. The Arterial System • Aortic system and pulmonary system. • Aortic System – includes aortic arch and its branches. Arch rises from right anterior towards left, then runs backward as dorsal aorta along mid-dorsal line. • 1. Coronary arteries – supply blood to wall of heart. • 2. Innominate artery – • (i) Right common carotid artery – supplies blood to right side of brain. • (ii) Right subclavian artery – (a-right mammary artery – supplies blood to mammary glands & b-brachial artery – supplies blood to right forearm. • Left common carotid artery – supplies blood to left side of head. • Left subclavian artery – supplies blood to left forearm.

8. 5. Intercostal arteries – supply blood to intercostal muscles. 6. Phrenic arteries – supply blood to diaphragm. 7. Coeliac artery – (i) hepatic artery – blood to liver. (ii) gastric artery – blood to stomach. (iii) Lienal artery – blood to spleen and pancreas. 8. Anterior mesenteric artery – blood to duodenum, ileum, caecum and colon. 9. Renal arteries – blood to kidneys. 10. Genital arteries – blood to ovaries and Fallopian tubes. 11. ILio-lumbar arteries – blood to abdomen. 12. Posterior mesenteric artery – blood to hind part of colon and rectum.

9. 13. Common iliac arteries – (i) internal iliac artery – blood to dorsal pelvic cavity. (ii) external iliac artery (vesico-uterine artery – blood to urinary bladder and uterine artery and posterior Epigastric artery – blood to ventral abdomen). (iii) femoral artery – blood to hind-limb. 14. Sacral or caudal artery – blood to tail. 15. Lumbar arteries – carry blood to lung. B. Pulmonary system – includes pulmonary arch (bifurcates into right and left pulmonary arteries in the left auricle). Ligamentum arteriosum (connects aortic & pulmonary arches). Ductus arteriosus – passage between the two vessels in embryo.

10. The venous system of rat

11. 2. The Venous System • Four divisions : venae cavae system, portal system, pulmonary system and coronary system. • System of venae cavae – includes three vessels : • 1. Left Anterior Vena Cava – recieves 6 veins (internal jugular, external jugular – blood from face & ear, subclavian - blood from forelimb & shoulder, mammary – blood from mammary glands, intercostal – blood from intercostal muscles & azygos). • 2. Right Anterior Vena Cava. • 3. Posterior Vena Cava – starts as caudal or sacral vein, recieves veins (common iliac veins – femoral vein’ vesiaco uterine vein & posterior epigastric vein, ilio lumbar veins, genital veins, renal veins, hepatic veins).

12. B. Portal System – in rat, hepatic portal system, includes single large vein – hepatic portal vein. Recieves 4 tributaries: 1. Lieno-gastric vein – collects blood from stomach & spleen. 2. Duodenal vein – blood from duodenum & pancreas. 3. Anterior mesentric vein – blood from ileum, caecum, colon & rectum. 4. Posterior mesentric vein – blood from rectum. Significance - Hepatic Portal System • Brings digested food with blood to liver. • Liver stores sugar for future use. • Deaminates excess proteins.

13. Blood • Structure – fluid tissue, forms 6-10 % of body weight, opaque, sticky, salty & a mild alkaline reaction, pH about 7.4, osmotic pressure – 7 atmospheres, bright red (oxygenated), purple (deoxygenated), contains plasma (contains corpulses – red, white & platelets). • (a)Plasma – faint yellow liquid, 90% of it is water, contains inorganic salts and blood proteins. The salts include chlorides, carbonates, sulphates & phosphates. Other things dissolved : food, waste products, gases, hormones, vitamins, enzymes & antibodies. Hydrostatic pressure – pressure forcing substances into tissue fluid. Hydrostatic pressure – highest at arterial end, Osmotic pressure – highest at venous end.

14. (b) Red Corpulses – circular, biconcave, denucleated discs, bounded by elastic plasma membrane, have homologous cytoplasm. Cytoplasm contains haemoglobin and inorganic ions, impart red colour to blood. Rouleaux – piles of red corpulses. (c) White corpulses – irregular shape , colourless, nucleated. Diapedesis – red corpulses passing out of capillaries. 2 main types : non-granular leucocytes (monocytes, lymphocytes) & granular leucocytes (basophils, eosinophils, neutrophils). (d) Blood Platelets – rounded or oval, non-nucleated, granular, destroyed by phagocytosis in blood, aid in blood clotting. Haemopoiesis – formation of new blood corpulses.

15. Functions of blood • Plasma – takes digested food from intestine to body, collects CO2 from tissues & brings it to lungs, carries urea from liver to kidneys, transports hormones, supplies materials to glands, regulates water balance, regulates pH of body fluids, equalizes body temperature, keeps al tissues moist. • Red corpulses – carry oxygen from lungs to tissues. • White corpulses – act as soldiers, scavengers & builders of body, heal wounds. • Blood platelets – help in blood clotting.

16. II. Lymphatic System • Comprise of lymph, network of fine channels, lymphatic vessels & lymphatic nodes. • Lymph – two parts : plasma & white corpulses. Hands over food, oxygen & hormones from blood to tissue cells, & waste materials from tissue cells to blood. • Lymphatic Capillaries – from intercellular spaces, tissue fluid passes into lymphatic capillaries. • Lymphatic Vessels – lymphatic capillaries join to form these vessels, lymphatic vessels join to form – thoracic duct & right lymphatic duct. • Lymphatic nodes – occur at intervals in course of lymphatic vessels, rich in white corpulses, remove bacteria from lymph.

17. Spleen Structure – elongated, curved, dark-red organ attached to posterior border of stomach by gastro-splenic omentum. Functions – Macrophages (certain cells of spleen) destroy worn-out red corpulses & foreign germs, stores, releases & produces new red and white corpulses.