Cardiovascular System - midterm 2 Flashcards
Heart
- in a cavity called the mediastinum (= spaces between lungs within thoracic cavity)
Coverings = Pericardium
- double-walled sac surrounding heart
- 3 layers
- between pericardial layers = pericardial cavity with serous fluid (lubricates)
Pericardium 3 layers:
a) fibrous pericardium
- outermost layer = dense irregular CT
- anchors to surrounding structures e.g. diaphragm, great vessels (aorta, vena cava, etc)
b) serous pericardium - 2 parts:
i. parietal pericardium (fibrous pericardium and partietal pericardium = pericardial sac)
ii. visceral pericardium (= epicardium)
- fused to heart surface, so is part of heart wall
Heart wall (3 parts)
a) epicardium
- stratified squamous epithelium and CT
b) myocardium
- = cardiac muscle
- arranged in spiral/circular pattern, reinforced with CT
c) endocardium
- simple squamous epithelium and CT
- epithelium named endothelium - lines inner surface of heart and ALL blood vessels
Chambers and associated blood vessels
a) Right Atrium
- inferior and superior vena cava
- coronary sinus (posterior)
b) Left Atrium
- 4 pulmonary veins
c) Right Ventricle
- pulmonary trunk - divides to form 2 pulmonary arteries
d) Left Ventricle
- aorta
Septa (separate chambers)
a) interatrial septum
- separates atria
b) interventricular septum
- separates ventricles
- deep to inter ventricular sulcus (external)
Fibrous skeleton
- CT fibres around the muscle fibres + CT rings between atria & ventricles at the coronary sulcus
- allows openings to remain open at all times (valves open + close)
- provides electrical insulation - prevents simultaneous contraction of chambers
Atrioventricular (AV) valves
i. bicuspid (mitral) valve
- left side - 2 cusps
ii. tricuspid valve
- right side - 3 cusps
- Chordae tendineae (CT) attach AV valve cusps to papillary muscles (projections of myocardium) - prevent eversion of cusps
Semilunar valves
3 cusps each
i. aortic - separates left ventricle + aorta
ii. pulmonary - separates right ventricle + pulmonary trunk
Cardiac Muscle Cells
- form BOTH contractile myocardium + conduction system
- similarities to skeletal muscle:
a) striated (myofibrils with sarcomeres)
b) has sarcoplasmic reticulum & T-tubules - differences:
a) branched (myofibrils with sarcomeres)
b) uninucleated
c) intercalated discs = region where 2 fibres meet - contain anchoring and gap junctions
Conduction System
- cardiac muscle cells modified to produce and conduct electrical impulses - DO NOT CONTRACT
- have 5 parts
- note: electrical signal spreads from conduction system to contractile cardiac cells when they contract
Conduction system parts:
a) sinoatrial (SA) node
- in right atrium at base of superior vena cava
- generates impulses the fastest - sets pace
b) atrioventricular (AV) node
- base of right atrium
c) Bundle of His
- superior part of interventricular septum
- electrically connects atria to ventricles
d) Bundle of His Branches
- go to each ventricle
e) Purkinje fibers
- terminal fibers in ventricles only
Circulatory Routes
closed, double circulation
- closed = blood confined to heart + blood vessels
- double = 2 routes (pulmonary + systemic)
Adult Circulation: Pulmonary circulation-
- right ventricle to lungs via pulmonary arteries (deoxy blood)
- pick up oxygen in lungs via capillaries
- lungs to left atria via pulmonary veins (oxygenated blood)
Adult Circulation: Systemic Circulation-
- left ventricle to organs via aorta (oxygenated)
- organs remove oxygen via capillaries
- organs to right atrium = systemic circulation > subdivisions/subroutes: - cerebral = brain
hepatic = liver
coronary = heart
Adult Circulation: Coronary Circulation (visible externally)
see figure
Fetal Circulation
- fetus gets O2, nutrients from + expels wastes to mothers blood
- exchange site in placenta
differences in fetal circulation from adult circulation
a) umbilical vein (towards the fetal heart)
- carries oxygenated blood from placenta to vena cava
b) lungs + liver basically non functional
c) umbilical arteries (away from fetal heart
what shunts are bypassed in fetal circulation
i. ductus venosus
ii. foramen ovale
iii. ductus arteriosus
general structure of blood vessels (except capillaries)
1) Tunica Externa - CT
2) Tunica media
- smooth muscle
- elastic fibers
3) Tunica intima/intena
- endothelium - simple squamous epithelium
4) Lumen - contains blood
