21 4 2 Mammalian Circulatory System The flow

21. 4. 2 Mammalian Circulatory System The flow of blood is maintained in 3 ways: 1 The pumping action of the heart arteries and capillaries 2 Contraction of skeletal muscles veins (aided by valves) 3 Inspiratory movements draws blood into the heart by the reduced pressure

General plan of the mammalian circulatory system

How blood flows: the circulatory system

The mammalian circulatory plan

How blood flows: the circulatory system Complete circulation consists of two pathways: pulmonary (lung) circulation & systemic (body) circulation

How blood flows: the circulatory system heart: coronary arteries & veins kidney: renal arteries & veins liver: hepatic artery & vein; hepatic portal vein (from gut)

How blood flows: the circulatory system aorta: aortic arch & dorsal aorta venae cavae: superior (from head) & inferior (from body) Usually arteries are oxygenated, veins are deoxygenated

Structure of the mammalian heart

Foetal circulation

The mammalian heart lung heart liver stomach Our hearts are protected by our rib cages

The mammalian heart

superior vena cava aorta pulmonary artery pulmonary veins left auricle right ventricle inferior vena cava coronary artery coronary vein left ventricle

21. 5 Heart Structure & Action 21. 5. 1 Structure of the Mammalian Heart - Pericardium: membrane of the heart - Cardiac muscles works (contracts) for 24 hours without rest - Coronary artery provides nutrients & oxygen to cardiac muscles Coronary veins carry away wastes and carbon dioxide from heart muscles - Interventricular septum divides the heart into right and left halves - The heart is divided into 4 chambers: - The left & right auricles (atria) and - The left & right ventricles

Auricles - Left & right auricles receive blood from veins and drain blood into the ventricles; - have thinner walls than ventricles - Right auricle receives deoxygenated blood from venae cavae (superior & inferior) - Left auricle receives oxygenated blood from pulmonary veins

Ventricles - pumps blood to all parts of the body; have thicker, more muscular walls than the auricles - Right ventricle pumps deoxygenated blood to the lungs through the pulmonary artery - Left ventricle pumps oxygenated blood into the aorta to deliver blood around the body (except the lungs) - Left ventricle has thicker wall than right ventricle because it has to pump blood all around the body, while the right ventricle only pumps blood to the lungs which are very close to the heart

Valves - enable blood to flow in only one direction: 1. Tricuspid valve: between right auricle and right ventricle 2. Bicuspid valve: between left auricle and left ventricle Both are attached by heart tendon to the muscular walls of ventricles in order to prevent the valves from being turned inside out 3. Semilunar valves: prevents blood flowing back from aorta and pulmonary artery tendon valve

21. 5. 2 Control of Heart Beat (Cardiac Cycle) All vertebrates are myogenic, i. e. the heart beat is initiated from within the heart muscle itself rather than a nerve impulse out it. Neurogenic means the heart beat is initiated by nerves, e. g. in insects. The electronic heart pacemaker (SA node)

Nucleus Connective tissue Cardiac muscle (LS) Fibre with striations

Sino-atrial node (SA node) - located in wall of R A near the vena cava 'pace-maker' which determines the basic rate of heart beat: - wave of contraction from SA node both atria atrio-ventricular (AV) node Purkinje fibres (bundle of His) apex of ventricles contraction from ventricular apex upwards

n Cardiac Cycle

Cardiac Cycle n Systole - heart contraction n Diastole - heart relaxation n

21. 5. 3 Factors Modifying Heart Beat Cardiac output: Volume of blood pumped at heart beat x no. of beats/unit time - controlled by medulla oblongata by 2 centres: cardio-acceleratory centre (sympathetic) and cardio-inhibitory centre (parasympathetic)

During heavy exercise: CO 2 p. H chemoreceptor in carotid artery cardio-acceleratory centre heart beat (to remove more CO 2) until CO 2 (p. H ) detected by carotid receptors cardio-inhitory centre heart beat

also: stretch receptors in aorta, carotid artery stimulated cardio-inhibitory centre heart beat stretch receptors in vena cava stimulated cardio-acceleratory centre heart beat

21. 5. 4 Maintenance & Control of Blood Pressure vasoconstriction: blood vessels narrowed blood pressure vasodilation: blood vessels dilated blood pressure Both controlled by vaso-motor centre in medulla oblongata arterioles in body (constrict/dilate) baroreceptors: pressure receptors in carotid artery detect blood pressure changes and relay impulses to the vaso-motor centre

examples: blood pressure baroreceptors vaso-motor centre sympathetic nerve arterioles vasoconstriction b p

blood pressure baroreceptors vaso-motor centre parasympathetic nerve arterioles vasodilation b p

Factors causing blood pressure increases: 1. CO 2 blood pressure speed to deliver blood to heart remove more carbon dioxide 2. Hormones, e. g. adrenaline raises blood pressure

Pressure changes in the atria, ventricles & aorta during one cardiac cycle

21. 5. 5 Heart Disease - coronary heart disease 1. Coronary thrombosis - a blood clot blocking the coronary vessel Wall of artery Thrombus (clot) Plaque on inner wall of artery

21. 5. 5 Heart Disease - coronary heart disease 1. Coronary thrombosis - a blood clot blocking the coronary vessel 2. Atherosclerosis (hardening of the arteries) - barrowing of the arteries due to fat, fibrous, or salt deposits 3. Spasm - repeated contractions of the muscles in the coronary attery walls

Heart attack Cholesterol, Narrows the lumen in arteries, Decreases blood supply to organs smooth lining blood flow restricted artery blocked by blood clot fatty & fibrous deposits 血液中的脂肪物質如膽固醇, 積聚在動脈的內壁, 便會使動脈內腔變窄, 繼而使這些動脈提供給器 官的血液減少。

The human lymphatic system

n The lymphatic system It consists of lymph vessels with lymph. n

21. 6 Lymphatic System 21. 6. 1 Tissue fluid and its formation - composition same as blood but without RBCs, platelets & proteins because they are too large to leak out of the capillaries - forms a link between blood and cells, providing a medium for exchange of materials between blood & cells

Exchange of materials between blood & body cells

Lymph some tissue fluid returns to capillaries by osmosis while some (about 10%) goes into lymph capillaries; this fluid is now called lymph Path: Blood lymph capillaries lymph vessels lymph ducts Blood - Lymph re-enters blood

Formation and destination of tissue fluid

At the arterial end of a capillary, liquid is forced out as tissue fluid which is similar to plasma in composition except its has no plasma proteins, platelets & RBCs. At the venous end, some fluid returns to blood while some enters lymph vessels which eventually join to a vein near the heart and thus returns to blood finally.

Lymph is driven by contraction of surrounding muscles, aided by valves which enable one-way flow to the neck.

Lymph nodes - filter lymph passing through; with numerous WBCs to kill bacteria or neutralize toxins for bodily defence - during infection these nodes frequently swell - major sites of lymphocytes production

Movement of lymph through the lymphatic system: 1. Hydrostatic pressure 2. Muscle contraction 3. Inspiratory movement 4. Valves to ensure one-way traffic towards the heart

Lymphatic System and the Circulatory System

Functions of the lymphatic system 1 Transport of tissue fluid back into the blood circulation 2 Transport of fat from intestinal villi 3 As a bridge for the exchange of materials between capillaries and tissue cells 4 As a site for body defence (lymph nodes with WBCs)