Chapter 21: The Cardiovascular System

what does the heart keep in motion

blood, if blood stops moving, nutrient and oxygen supplies are exhausted and wastes accumulate

how many times does the heart beat per day

100,000 times per day which is about 70 beats per minute

how much blood does the heart pump

1.5 million gallons of blood per year, which is about 2.9 gallons per minutes, however, the heart pumps between 5 and 30 L of blood, it can vary widely

what size is the heart

the size of a clenched fist

how many chambers does the heart have 

4 

4 chambers of the heart

2 atria and 2 ventricles

where does the heart pump blood

into two circuits

2 circuits

pulmonary circuit (to lungs) and systemic circuit (to rest of body)

arteries 

transport blood away from the heart 

veins

transport blood toward the heart

capillaries

vessels that interconnect arteries and veins

what is the heart surrounded by

pericardium

two parts of pericardium 

outer fibrous pericardium and inner serous pericardium 

inner serous pericardium consists of two layers

visceral layer and parietal layer

visceral layer

inner, also called epicardium, is attached to the surface of the heart

parietal layer

outer, adjacent to fibrous pericardium

pericardial cavity 

space between the two serous layers containing pericardial fluid 

pericardial fluid 

lubricates the space to reduce friction 

what do the walls of the heart consist of

three layers, epicardium, myocardium, and endocardium

epicardium

external surface, consists of visceral pericardium

myocardium

consists of cardiac tissue, including cardiac muscle cells, connective tissue, blood vessels, and nerves

endocardium

internal, endothelial surface

what kind of appearance does cardiac muscle tissue have 

striated 

what is cardiac muscle tissue dependent on

aerobic respiration allows lots of mitochondria and myoglobin

what is circulatory supply of cardiac muscle tissue

very extensive

how do cardiac muscle cells contract

without information come from the CNS (involuntary)

how are cardiac muscle cells interconnected 

by intercalated discs 

what do cardiac cells have

cell to cell junctions

how are plasma membranes of two adjacent cardiac cells bound together

by desmosomes

what do the intercalated discs bind

myofibrils of adjacent cells together

how are cardiac muscle cells connected 

by gap junctions 

gap junctions

ions move directly from one cell to another creating a direct, electrical connection, allows all the muscle cells to form a functional syncytium (contract as one unit)

what is each cardiac cell wrapped in

an elastic sheath

what is each muscle layer wrapped in

a fibrous sheet

fibrous sheets 

separate the superficial layer from the deep layer muscles

where do fibrous sheets encircle

base of the pulmonary trunk, ascending aorta, and valves

what does the cardiac skeleton stabilize

position of the cardiac cells and position of the heart valves

what does the cardiac skeleton provide support for

blood vessels and nerves in myocardium

what does the cardiac skeleton help distribute 

forces of contraction

what does the cardiac skeleton help prevent

overexpansion of the heart

what does the cardiac skeleton provide elasticity for 

so the heart recoils after contraction 

what does the cardiac skeleton isolate

atrial cells from ventricular cells 

where does the heart like 

slightly left of midsaggital plane 

where is the heart located

mediastinum

base of heart

superior border of heart

apex

inferior portion of heart

right border 

formed only by the right atrium 

inferior border

formed by the right ventricle

anterior surface

consists of the right atrium, right ventricle, and left ventricle

posterior surface

consists of the left atrium, and a small portion of the right atrium

diaphragmatic surface 

composed of the right and left ventricles 

how can the four chambers of the heart be identified

by sulk (grooves) on the external surface

interatrial grooves

separates the left and right atria

coronary sulcus

separates the atria and the ventricles 

anterior inter ventricular sulcus 

separates the left and right ventricles 

posteror interventricular surfaces

also separates the left and right ventricles

how are the left and right atria positioned

superior to coronary sulcus

left and right atria both have

thin walls

auricle 

left and right atria contain an expendable anterior portion called an auricle 

how are the left and right ventricles positioned

inferior to the coronary sulcus

what do the left and right ventricles have

thicker walls than the atria

left ventricular wall

is thicker than the right ventricular wall because it pumps to the body

interatrial septum 

separates left and right atria 

interventricular septum

separates left and right ventricles

how are atrioventricular valves formed

from folds of endocardium

where are the atrioventricular valves situated between

atria and ventricles

what does the right atrium receive 

oxygen poor venous blood via the superior vena cava, inferior vena cava, and coronary sinus 

how does the coronary sinus enter the right atrium

from the posterior side

what does the right atrium contain

pectinate muscles in anterior wall and auricle

what does interatrial septum contain

fossa ovalis

fossa ovalis 

fetal remnant of the foramen vale that allowed fetal blood to bypass the lungs 

what does the right ventricle receive

receives oxygen poor blood from the right atrium

how does blood enter the right ventricle

by passing through the right atrioventricular valve which is also called the right AV valves or tricuspid valve

how does blood leave the right ventricle

by passing through the pulmonary valve, which is also called the pulmonary semilunar valve, and leads to the pulmonary trunk then to the right and left pulmonary arteries

how is the right AV valve connected to papillary muscles 

via chordae tendinae

chordae tendinae

there are three fibrous cusps and three papillary muscles, each of the three cusps is connected by the chordae tendinae to separate papillary muscles

what do papillary muscles and chordae tendinae prevent 

valve inversion when the ventricles contract 

what does the internal surface of the right ventricle consist of

trabeculae carneae and moderator band

trabeculae carneae

muscular ridges

moderator band

only found in the right ventricle, muscular band that extends from the interventricular septum to the ventricular wall and prevents over expansion of the thin walled right ventricle

what does the left atrium receive 

oxygenated blood from the lungs via the right and left pulmonary veins 

what are pectinate muscles restricted to in the left atrium

auricle

how does blood pass in the left atrium

through the left atrioventricular valve also called the bicuspid valve, left AV valve, or mitral valve

why does the left ventricle have the thickest wall

its needed for strong contractions to pump blood throughout the entire systemic circuit compare to the right ventricle which has a thin wall since it only pumps blood through the pulmonary circuit

what does the left ventricle not have 

moderator band

the left ventricle has prominent

trabeculae carneae

chordae tendinae in left ventricle

connecting to two cusps and two papillary muscles

how does blood leave the left ventricle

by passing through the aortic valve

aortic valve 

also called aortic semilunar valve, blood enters the ascending aorta and blood then travels to the aortic arch and then down the descending aorta and to all body parts (systemic) 

structural differences in the right ventricle

thinner wall, weaker contraction, and has a moderator band

structural differences in the left ventricle

thicker wall, powerful contraction, and six to seven times more powerful than the right ventricle

how many valves are in the heart

4

4 valves of the heart 

two AV valves (triscuspid and bicuspid valves) and two semilunar valves (aortic and pulmonary valves)

what 4 parts are AV valves composed of

ring of connective tissue that connects to heart tissue and is part of fibrous skeleton of the heart, cusps, chordae tendinae which connect to cusps and papillary muscles, and papillary muscles that contract in such a manner to prevent AV valve inversion

how does the AV valve function during the cardiac cycle

papillary muscles relax, due to pressure in the atria AV valves open and blood flows from atria to ventricle

what happens when ventricles contract

pressures caused the AV valves to close and semilunar valves to open

regurgitation 

closure of AV valves prevents regurgitation or backflow into the atria which forces blood through the opening of semilunar valves 

where do coronary blood vessels originate

base of ascending aorta

coronary circulation

supply the cardiac muscle tissue via the coronary circulation

right coronary artery

atrial branches, right marginal branch, posterior interventricular branch, passes between the right auricle and pulmonary trunk, conducting system branches