UF APK2100C CH 19-25

Heart

- muscular double pump

- upside down backwards leaning cone

The right heart pumps blood into the ____________ while the left heart sends blood to the __________

- pulmonary circuit

- systemic circuit

Diaphragm

- forms the floor of the thoracic cavity and seals off the thorax from the lower abdominal cavity

- primary muscle of inspiration

Pleura cavity

- contains the left and right lungs

Mediastinum

- region running down the center of the thoracic cavity between the left and right pleural cavities

- contains the heart

Layers of the heart wall

- epicardium

- myocardium

- endocardium

Epicardium: def, tissue

- outermost layer of the heart which is the same as the visceral layer of the pericardium

- simple squamous epithelium= *mesothelium*

Myocardium

- thickest layer, made from cardiac muscle tissue

Endocardium: function, tissue

- inner most layer that lines the chambers and covers the valves

- simple squamous epithelium that becomes continuous with the simple squamous epithelium lining the blood vessels (endothelium)

Pericardium

- 3 layered serous membrane covering the heart

Layers of the pericardium

- fibrous pericardium

- parietal pericardium

- visceral pericardium

Fibrous pericardium: def, function, tissue

- outer most layer of the pericardium

- adheres to the diaphragm and root of large vessel

-dense connective tissue

Parietal pericardium: def, characteristics

- adheres to the inner surface of the fibrous pericardium

- not in direct contact with the heart itself

Visceral pericardium

- epicardium; *touches the myocardium*

Pericardial cavity

- space between the visceral pericardium and the parietal pericardium that contains serous fluid

Cardiac muscle bundles: definition, function

- circularly arranged bands of smooth muscle that envelope the two atrial chambers and drop down to form the ventricular walls

- decreases the size of the lumen during contraction and directs blood flow

Cardiac skeleton

- connective tissue outline for cardiac myocytes

Atria: def, location

- smaller superior chambers that receives blood from veins

- posteriorly placed

Interatrial septum

- piece of the wall of the myocardium (cardiac skeleton) that assures the blood is separate in atria

Ventricles

- larger, thicker walled inferior chambers

Interventricular septum: def, made from

- piece of the wall of the myocardium that assures the blood is separate in ventricles

- made largely from the wall of the left ventricle

Coronary sulcus

- groove that encircles the entire circumference of the heart

- delineates the atria from ventricles and houses major coronary arteries and veins

Anterior interventricular sulcus

- runs along the interventricular septum on the front of the heart

- houses coronary arteries and veins

Posterior interventricular sulcus

- sulcus on the back of the heart that houses coronary arteries and veins

Auricles

- ear like hollow pouches

- right and left

- equivalent to atria

Pulmonary trunk

- branches into the right and left pulmonary arteries

Coronary sinus

- large vein on the back of the heart that drains the heart and dumps into the right atrium

Pulmonary veins

- 4 (2 right, 2 left)

- delivers oxygenated blood from the lungs to the heart to dump into the left atrium

Pulmonary arteries

- 2

- delivers deoxygenated blood from the heart to the lungs

The posterior wall of the atria are ________

smooth

Pectinate muscles

- cone like horizontal ridges in both atria located anteriorly

Crista terminalis

- c shaped ridge in the atria that forms at the opening of the superior and inferior vena cava

Fossa Ovalis: def, function

- darkned oval that is a remnant of the foramen ovale that is present in fetuses in the interatrial septum

- acts as a blood shunt before we are born to allow blood to switch from the left and right sides of the heart

Differences between the wall of the ventricles and the atria

- walls of the ventricles are more meaty and have *more ridges*

Trabeculae carneae

- meaty ridges of the ventricles made from *cardiac tissue*

- project up and form mound like structures

Papillary muscles

- mound like structures formed from the trabeculae carneae

Chordae Tendineae

- strings of connective tissue coming from the valves of the atria that attach to the papillary muscles

What happens to the papillary muscles and chordae tendineae when the heart contracts?

- papillary muscles contract downwards and pulls the chordae tendineae tight which prevents the valve from flapping upwards into the atria

Atrioventricular valves (AV): def, includes/def

- valves allow one way blood flow from the atria to the ventricles

- tricuspid valve: right heart

- bicuspid valve/mitral valve: left heart

Semilunar valves: def, includes

- blood is pumped out of the ventricles through these valves, into the pulmonary or systemic circuits

- pulmonary and aortic semilunar valves

Pulmonary semilunar valves

- allows blood to pass from the right ventricle out into the pulmonary trunk

Aortic semilunar valves

- allows blood from the left ventricle, through the valve up into the aorta

The majority of the left ventricle is in contact with the _____________

- diaphragm

Differences between the right and left ventricles? Why?

- thicker myocardium of left ventricle

-blood from the left ventricle must travel far to all parts of the body (not just lungs) so the thicker myocardium allows the left ventricle to generate a larger pressure

_____________ is the most anterior valve and ___________ is the most anterior vessel

- pulmonary semilunar valve

- pulmonary trunk

Heart valves: anterior to posterior

- pulmonary valve

- aortic valve

- mitral and tricuspid valve

AV during diastole and systole

- blood comes from the atria through open AV; chordae tendinae are loose and papillary muscles are relaxed

- during contraction the blood shoots up and can go back into the atria or to the vessel

- AV catches the blood pushed from the ventricles in its flaps; papillary muscles contract down, chordae tendineae pull down to anchor edges of valve flaps to prevent backflow

Semilunar valves during diastole to systole

- contraction of ventricle pushes blood up through the valves to open them

- when blood falls back into the cusps they push them close to prevent backflow

Where does the right atrium receive blood from? Deoxygenated or oxygenated blood

- superior vena cava

- inferior vena cava

- coronary sinus

- deoxygenated

Depolarization

- electrical event that triggers the contraction in the myocardium

SA node: def, function, location

- collection of cardiac myocytes that function to generate a spontaneous depolarization

- natural pacemaker of the heart

- located in superior right atrium

AV node: def, function, location

- collection of cardiac myocytes that can spontaneously depolarize to trigger a contraction, but occurs much slower than the SA node

- activated by the SA node

- located in inferior right atrium

Where does the electrical signal travel after it is produced in the SA node?

- AV node

- bundle of His

- bundle branches

- Purkinje fibers

What is the terminal point of the electrical conduction system?

- Purkinje fibers

From the bundle branches to the purkinje fibers the cardiac myocytes are extremely ________ and ___________ relative to other myocytes because they _________

- large (in diameter) and long

- send the signal quickly (NOT CONTRACT)

What supplies oxygen to the heart?

- coronary vessels outside of the heart

Coronary arteries: location, function

- stem from base of aorta and are the main arteries that supply the myocardium

Right coronary artery

- sits in the coronary sulcus and encircles the heart

Right marginal artery

- branch of the right coronary artery that extends inferiorly down to the apex

Left Coronary artery

- originates behind the pulmonary trunk (still anterior) and peaks out from the left auricle and immediately bifurcates

Anterior interventricular artery

- branch of the left coronary artery that travels in the interventricular septum

Circumflex artery

- branch of the left coronary artery that bends around the back of the heart and meets up with the right coronary artery to form a junction point

Anastomosis: def, function

- junction point of vessels

- functions to provide an alternative route for blood in the event of a blockage

Posterior interventricular artery

- runs along the posterior interventricular sulcus that forms an anastomosis when joining with the right coronary artery

Small cardiac vein

- runs directly beside the right marginal artery

- when it approaches the coronary sulcus it travels with the right main coronary artery along the posterior surface of the coronary sulcus to dump into the coronary sinus

Middle cardiac vein

- runs along the posterior interventricular sulcus and dumps into the coronary sinus

Great cardiac vein

- runs with *both branches* of the left main coronary artery and dumps into the coronary sinus

Atherosclerosis: def, characteristics

- fatty deposits in the inner lining of the arteries that can occlude blood flow

- plaque decreases the size of the lumen

Angina pectoris

- chest pain from tissue hypoxia in the myocardium or *spastic coronary artery* (from atherosclerosis)

Blood flow after leaving the heart

- blood leaves the heart through arteries that get smaller and smaller until they become capillaries

- blood flows out of capillaries into small veins that get larger and larger as it returns to the heart

Layers of the vessel wall, difference between arteries and veins?

- Tunica intima, tunica mediam and tunica externa (adventitia)

- arteries and veins have the same layers just different thickness

Tunica intima: def, tissue, characteristics, differences

- innermost layer made of simple squamous epithelium

- *continuous with the endocardium*

- identical thickness in arteries and veins

Tunica media: def, tissue, function, differences

- middle layer made of circularly arranged smooth muscle

- contracts to decrease the size of the lumen

- thicker in arteries than veins

Tunica externa (adventitia): def, tissue, function, differences

- outer layer

- connective tissue

- helps adhere vessels to whatever structure they are running alongside

- thicker in veins than arteries

Function of tunica externa in veins

- protects the structure and gives support in veins due to the thin tunica media

Vasa Vasorum

- little blood vessels in the tunica externa that supply some of the muscular tissue in the wall of that vessel

- present in both

At the same level the lumen of the vein is _________

- larger

Venous valve: def, function

- one way valves only present in veins

- opens as blood pushes against it and closes when blood falls down from low pressure to prevent backflow of blood

Capillaries

- smallest type of blood vessel composed of 2 layers: tunica intima, and basement membrane

Basement membrane

- thin extracellular connective tissue that helps adherence and doesn't impede gas diffuson

Capillary network

- mesh like structures of tiny capillaries

Arteries: def, exception

- carry oxygenated blood blood away from the heart

- pulmonary arteries- carry deoxygenated blood from the heart to the lungs

Types of arteries

- elastic

- muscular

- arterioles

Elastic arteries: def, function, example

- arteries containing large lumens and lots of elastin

- receives large boluses of blood

- aorta and its branches

Muscular arteries

- thick tunica media to maintain pressure

Arterioles

- extremely small arteries that lead into the capillaries

Arterioles are able to vasoconstrict and dilate because of their ___________

- tunica media

_________________ is always present in the arteriolar wall and enables contraction and dilation

- smooth muscle tone

The size of the capillaries are ___________ compared to the red blood cells that pass through it

- small

How do RBC pass through the capillaries? Why?

- single file line

- enhances the contact of the RBC with the wall of the capillaries because gas exchange only occurs when they are in full contact

Terminal arteriole

- last arteriole before it branches into a capillary bed

Metarteriole

- arteriole that travels down the middle of the capillary bed and transitions into a different channel when it reaches the venous side

Thoroughfare channel

- what the metarteriole transitions into once it is on the venous side of the capillary bed

Vascular shunt: def, function

- made up of the metarteriole and thoroughfare channel

- allows blood to bypass capillaries and flow from the arteriole to the venule in the capillary bed

Precapillary sphincters:def, function, location

- circularly arranged smooth muscle cells wrapped around the base of capillary branches

- contraction allows blood to shunt to the venous side instead of supplying tissues

- *mesenteric vasculature (intestines)*

Why are precapillary sphincters necessary?

- Allows for the redistribution of blood flow to organs that are working harder

- cuts off blood flow to organs that don't need as much

- like during exercise

How do molecules pass into and out of the capillaries?

1. diffusion through endothelial cell membranes (simple diffusion for O2 and CO2)

2. intercellular clefts

3. pinocytotic vesicles

4. fenestrations

Intercellular clefts

- gap between the simple squamous epithelial cells that are *making up the endothelium*

Fenestrations

- holes or windows formed by 2 sides of epithelial cells that fuse together to form a pore

What is the exception to molecules passing through the capillaries?

- Blood brain barrier: complete tight junctions where glucose is ushered across the walls