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8 Breathing and Circulation > 8.5 The Heart > Flashcards

8.5 The Heart Flashcards

1
Q

Heart function:

A

Double pump: Right side: low resistance pulmonary circulation. Pressure=20mmHg
Left side: high resistance systemic circulation. Pressure=130mmHg

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2
Q

Heart structure:

A

Atria= chambers to receive blood (right receives from systemic). Ventricles= chambers to eject blood (right ejects to lungs).

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3
Q

Principle venous structures draining to the heart:

A

Superior and inferior venae cavae, pulmonary veins; coronary sinus. (SEE IMAGE)

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4
Q

Coronary sinus

A

Collection of vessels that collect blood from the heart. Just under and left of AV node. Route by which blood of heart drains into right atrium.

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5
Q

Situs inversus

A

the major visceral organs are reversed or mirrored from their normal positions. The positions are flipped, and the apex of the heart located on the
right side. The body develops as though flipped through the midline.

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6
Q

Pericardial sac

A

Surrounds heart. Sealed to the diaphragm and around the vessels entering and leaving the heart.

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7
Q

Principal arterial structures leaving the heart:

A

Aorta & pulmonary trunk. (SEE IMAGE)

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8
Q

Atria: Structural adaptation to function.

A

Right atrium: has a rough-walled part (arising from primitive atrium), smooth-walled part= derived incorporation of sinus venosus and developing interatrial septum.

Left atrium: receives blood from 4 pulmonary veins. Has a rough region (from primitive atrium) and smooth inflow region formed by incorporation of primitive pulmonary veins during development.

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9
Q

Valves: Structure

A

Leaflets of valves are anchored within the papillary muscles of the wall of heart by thin and tough structures= chordae tendinae!!!

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10
Q

Ventricles: Structural adaptation to function.

A

has rough parts to it [trabeculae carnae].

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11
Q

Positions of the atrioventricular, pulmonary, and aortic valves:

A

Atrioventricular valves: blood leaves left atrium via the bicuspid (mitral) atrioventricular valve. Blood leaves right atrium by tricuspid valve.

Outflow tract valves: 3 semilunar cusps with thickened margins. Reflux prevented by blood bulging cusps and pushing them together.

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12
Q

Principles and morphology of coronary vascular supply.

A

Right coronary artery usually provides the posterior interventricular artery, but this branch can come from the left coronary artery (“left dominant” heart). Left coronary artery is larger and more important. No anastomoses.

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13
Q

Principles of blood supply to myocardium:

A

RCA supplies right side and interatrial septum. LCA supplies left side and anterior interventricular septum and conducting system.

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14
Q

Angina.

A

Chest discomfort or shortness of breath caused when heart muscles receive insufficient oxygen-rich blood.

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15
Q

Myocardial ischaemia; consequences of occlusion of the major coronary arteries.

A

Myocardial infarction= cardiac muscle death. Anoxia- particularly on exertion.
LCA block: causes central chest pain which classically radiates down medial aspect of left arm. Ventricles may beat more slowly than atria because they’re disconnected from atrial pacemaker and beat with their own rhythm.

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16
Q

When does coronary perfusion occur?

A

during diastole.

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17
Q

Principles of conducting system of the heart.

A

Ensures optimal expulsive contraction of ventricular muscle.

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18
Q

What innervates the heart?

A

Vagus parasympathetic and sympathetic systems.

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19
Q

Sino-atrial node

A

acts as pacemaker, impulses spread through atria via the atrial muscle to the AV node. SA activity is modified by vagal (parasympathetic pre-ganglionic) and sympathetic postganglionic fibres which arise from cardiac plexuses beneath arch of aorta; vagal fibres end on ganglion cells near node.

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20
Q

Atrioventricular bundle:

A

Arise from AV node and pass through the fibrous skeleton. AV bundle divides into the right and left bundles which pass down either side of septum.

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21
Q

What innervates the heart?

A

Vagus parasympathetic and sympathetic systems.

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22
Q

Structure and functions of arteries

A

1) Elastic (aka conducting/large)= e.g., aorta. Subject to cyclic changes of blood pressure, high as the ventricles pump blood into the lumina and low between the emptying of these chambers. To compensate for these intermittent pressure alterations, an abundance of elastic fibres are located in the walls of these vessels. to provide structural stability and permit distention of the elastic arteries but also assisting in the maintenance of blood pressure in between heartbeats.
2) Muscular (aka distributing/medium)= comprise most of the named arteries distributing blood to various organs e.g femoral and carotoid. Their tunica media is composed mostly of many layers of smooth muscle cells.

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23
Q

What are portal systems? Where do they occur?

A

occurs when a capillary bed pools into another capillary bed through veins, without first going through the heart. e.g., in liver and pituitary gland.

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24
Q

Structure and functions of arterioles

A

smallest arteries, responsible for regulating blood pressure, characterized by the presence of incomplete rings of smooth muscle cells and supported by other cells called pericytes. Precapillary sphincters encircle the origins of the capillaries and contraction of these precapillary sphincters of the arteriole shunts the blood into the capillaries.

25
Q

Structure and functions of capillaries

A

form thin-walled networks that are supplied by arterioles and drained by venules. May be circumvented by arteriovenous anastomoses, interposed between the arterial and venous systems.
Composed of highly attenuated endothelial cells that form narrow vascular channels 8–10 micrometres in diameter and are usually less than 1mm long. Associated with capillaries are basal laminae and pericytes, but capillaries possess no smooth muscle cells- do not exhibit vasomotor activities. Control of blood flow into a capillary bed is established at the sites where individual capillaries arise from terminal arterioles and is accomplished by smooth muscle cells known as precapillary sphincters. Based on fine structural characteristics, three types of capillaries are recognized: fenestrated, continuous, and discontinuous.

26
Q

Continuous (non-fenestrated) capillaries

A

devoid of pores, and possess a continuous basal lamina. Material must traverse the endothelial cell either via pinocytotic vesicles or between endothelial cell junctions. In certain areas of the body (brain, thymus, testes), occluding junctions, formed by contiguous endothelial cells prevent the escape or entry of material through intercellular spaces.

27
Q

Fenestrated capillaries

A

possess numerous pores, usually bridged by diaphragms through which material can enter and leave the capillary lumen. These cells also possess pinocytic vesicles and are enveloped by a continuous basal lamina. Fenestrated capillaries are located in endocrine glands, pancreas, and lamina propria of the intestines, and they also constitute the glomeruli of the kidneys, although their fenestrae are not covered by a diaphragm.

28
Q

Discontinuous capillaries (sinusoids)

A

tortuous and possess large lumina. Their endothelial cells present large fenestrae and intercellular spaces, permitting leakage of material into and out of these vessels. Moreover, their basal lamina is not continuous. Frequently, macrophages are associated. Located in liver, spleen, lymph nodes, bone marrow, and the suprarenal cortex.

29
Q

Structure and functions of venules

A

Blood drains from the capillary bed into venules. Also responsible for the exchange of materials. Vasodilator substances (serotonin and histamine) appear to act on small venules, causing them to become “leaky” by increasing the intercellular distances between the contiguous endothelial cells. Most such intercellular gaps occur in small venules rather than in capillaries.
Capacitance vessels.

30
Q

Structure and functions of veins

A

conduct blood away from body tissues and back to the heart. Diameters are larger than those of corresponding arteries; however, veins are thinner walled, since they do not bear high blood pressures. Veins have fewer layers of smooth muscle cells in their tunica media than do arteries. Possess valves that act to prevent regurgitation of blood. Three categories of veins exist: small, medium, and large.

31
Q

Tunica intima, media, adventitia

A

Vessels are composed of three concentric layers: tunica intima, tunica media, and tunica adventitia.
The tunica intima is composed of a continuous sheet of simple squamous endothelial cells lining the lumen and of various amounts of sub-endothelial connective tissue. The tunica media, usually the thickest of the three layers, is composed of circularly arranged smooth muscle cells and fibroelastic connective tissue, whose elastic content increases greatly with the size of the vessel. The tunica adventitia is the outermost layer of the vessel wall, consisting of fibro-elastic connective tissue.

32
Q

Endothelial cells

A

Function in

(i) formation of a selectively permeable membrane
(ii) vasoconstriction
(iii) vasodilation
(iv) initiation of coagulation
(v) facilitation of transepithelial migration of inflammatory cells
(vi) angiogenesis
(vii) synthesis of growth factors
(viii) modifying Angiotensin 1 and oxidation of lipoproteins.

33
Q

Elastic and non-elastic vessels.

A

Elastic: compensate for intermittent pressure alterations. These elastic fibres provide structural stability and permit distention of the elastic arteries and assist in the maintenance of blood pressure in between heartbeats.

34
Q

Endothelial cell function: vasoconstriction

A
  • (sympathetic nerve fibres act on the smooth muscles of the tunica media but also: Endothelin 1, produced and released by endothelial cells of blood vessels).
35
Q

Endothelial cell function: vasodilation

A
  • parasympathetic nerve fibres in an indirect fashion. ACh binds receptors on the endothelial cells, inducing them to release nitric oxide. Nitric oxide acts on the cGMP system of the smooth muscle cells, causing their relaxation. Additionally, endothelial cells can produce prostacyclins, that induce the cAMP second messenger pathway in smooth muscle cells, affecting their relaxation.
36
Q

Endothelial cell function: vasodilation

A
  • parasympathetic nerve fibres in an indirect fashion. ACh binds receptors on the endothelial cells, inducing them to release nitric oxide. Nitric oxide acts on the cGMP system of the smooth muscle cells, causing their relaxation. Additionally, endothelial cells can produce prostacyclins, that induce the cAMP second messenger pathway in smooth muscle cells, affecting their relaxation.
37
Q

Endothelial cell function: initiation of coagulation

A
  • release tissue factor (also known as thromboplastin), an agent that facilitates entry into the common pathway of blood coagulation, and von Willebrand’s factor, which activates and facilitates the adhesion of platelets to the exposed laminin and collagens and induces them to release ADP and thrombospondin, which encourages their adhesion to each other and so clotting.
38
Q

Endothelial cell function: facilitation of transepithelial migration of inflammatory cells

A

When inflammatory cells have to leave the blood stream to enter the connective tissue spaces, endothelial cells express on their luminal plasma membranes E-selectins. These signalling molecules are recognized by carbohydrate ligands on the surface of the inflammatory cells, triggering their epithelial transmigration.

39
Q

Endothelial cell function: angiogenesis

A

New vessels arise from existing vessels due to the interactions of various signalling molecules, such as Angiopoietins 1 and 2, with specific receptors on endothelial cells that induce mitotic activity in pre-existing endothelial cells and recruit smooth muscle cells to form the tunica media of the developing vessels.

40
Q

Endothelial cell function: synthesis of growth factors

A

various colony-stimulating factors, which induce cells of blood lineage to undergo mitosis and produce various blood cells, and growth inhibitors, such as transforming growth factor.

41
Q

Endothelial cell function: modifying Angiotensin 1 and oxidation of lipoproteins.

A

produce angiotensin converting enzyme (ACE) which converts Angiotensin I to Angiotensin II, a powerful smooth muscle contractant and inducer of aldosterone release by the suprarenal cortex.

Also oxidize high cholesterol containing low density lipoproteins so that the oxidized by-product can be phagoytosed by macrophages.

42
Q

What is angiogenesis?

A

response to repair of damaged vessels, establishment of new vessels in repairing injuries, formation of new vessels subsequent to menstruation, formation of the corpus luteum, as well as in response to tumour formation.

43
Q

Major arteries carrying blood to the heart:

A

(SEE IMAGE)
Aorta: Ascending, arch, descending thoracic and abdominal aorta.
Brachiocephalic artery: Subclavian to upper limb and common carotid arteries; carotid bifurcation.
Common iliac: External iliac to lower limb; internal iliac (to pelvis, buttock, perineum). Pulmonary artery.

44
Q

Aortic aneurysm

A

bulge in the aorta.

45
Q

Ligamentum arteriosum

A

a small ligament that is the remnant of the ductus arteriosus formed within three weeks after birth

46
Q

Major veins carrying blood from the heart:

A

(SEE IMAGE)

Superior vena cava draining head and upper limbs; inferior vena cava draining abdomen pelvis and lower limbs.

47
Q

Organization and divisions of the mediastinum:

A

Superior

Inferior: anterior, middle (heart), posterior.

48
Q

Superior mediastinum

A

Base of neck. Contains oesophagus, trachea, major great vessels supplying head and neck, right brachiocephalic arteries, carotid and left subclavian arteries. Vagus passes around. The left vagus nerve passes around the ligamentum arteriosus, the left recurrent laryngeal nerve also present.

49
Q

Inferior mediastinum

A

Anterior: between sternum and pericardium, has lymph nodes.
Middle: heart and major vessels, phrenic nerves on outside of pericardium, hemi-azygous and azygous veins drain posterior thoracic wall.
Posterior: major structures all with vertical orientation in upright body, descending aorta, hemi-azygous veins and azygous veins.

50
Q

Position of great vessels:

A

(SEE IMAGE)
ascending aorta arises from left ventricle, which arches posteriorly over left pulmonary trunk and main bronchus towards the posterior thoracic wall. At the level of the 4th thoracic vertebra, the aortic arch becomes the descending aorta.

51
Q

What does thoracic duct do?

A

drains lymph into left subclavian vein.

52
Q

What is the hilum?

A

The mediastinal surface has a root or hilum where the bronchi, blood vessels, nerves and lymphatic vessels enter and leave the substance of the lung.

53
Q

Sympathetic system origin:

A

origin of preganglionic fibres from T1 -L2 of cord.

54
Q

Horner’s syndrome

A

(damage to sympathetic trunk at head of first rib affecting sympathetic innervation of the head)

55
Q

Where do sympathetic chain of ganglia affect?

A

effects on heart and airways.

56
Q

Where do thoracic splanchnic sympathetic nerves go?

A

to abdominal viscera

57
Q

Parasympathetic system composition and effects:

A

preganglionic fibres in vagus nerves; effects on heart and airways.

58
Q

Visceral afferent (sensory) fibres travel

A

travel with vagus and sympathetic nerves.

8 Breathing and Circulation (5 decks)

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