Heart

The Heart and Circulation

Cardiovascular System = Heart, Blood and Vessels

Lymphatic System = Lymph nodes, Organs and Vessels

Functions of Heart and Cardiovascular System

• Cardiovascular System– Bulk flow of blood– Exchange with tissue

• Heart– Right side receives oxygen-poor blood from

body tissues and pumps the blood to the lungs– Left side receives the oxygenated blood from

the lungs and pumps the blood throughout the body

Location of Heart in Chest

• Oblique Position• Apex = Left of Midline (5th ICS), Anterior to rest of heart• Base (posterior surface) sits on vertebral column• Superior Right = 3rd Costal Cartilage, 1” right midsternum• Superior Left = 2nd Costal Cartilage, 1” left midsternum• Inferior Right = 6th Costal Cartilage, 1” right midsternum• Inferior Left = 5th Intercostal Space at Midclavicular line

Pg 155

Cardiac Conduction

• Intrinsic system initiating and coordinating contraction of heart muscle– Sinoatrial node (where SVC enters RA)– Atrioventricular node (in atrioventricular

septum)– AV Bundle (in IV septum then splits)– Purkinje fibers (throughout LV)

• Cardiac Plexus (external innervation)– Vagus (parasympathetic)– Sympathetic trunk

pg 178

Pericardium

• Pericardium (3 layers)• 1) Outer-fibrous pericardium

– Serous pericardium• 2) parietal

• 3) visceral (epicardium)

• Pericardial Cavity– between layers of serous pericardium

– serous fluid

– lubricate heart while beating

pg 178

External Features of Heart

• Interventricular sulcus• Coronal/Coronary sulcus• Auricles of atria• Apex• Base• Coronary vessels• Ligamentum Arteriosum

Pg 158

The Great Vessels and major branches

Aorta (from Left Ventricle)

• Ascending– Coronary arteries

• Aortic Arch – Brachiocephalic trunk

– Left Common Carotid

– Left Subclavian

• Descending (Thoracic/Abdominal)– Many small branches to organs

Pulmonary Trunk (from Rt Ventricle)- -2 Pulmonary Arteries into lungs

Inferior/Superior Vena Cava

- Coronary sinus Pg 180

Layers of Heart

• Epicardium (most superficial)– Visceral serosa

• Myocardium (middle layer)– Cardiac muscle– Contracts

• Endocardium (inner)– Endothelium on CT– Lines the heart – Creates the valves

Fibrous Skeleton of Heart

• Insertion for cardiac muscle• Anchors valve cusps• Prevents valves from opening too much• Block electrical impulses from atria to ventricles• Contains AV node

Pg 170

Heart Chambers

• 2 receiving chambers:– Right atria

– Left atria

• 2 pumping chambers:– Right ventricle

– Left ventricle

Right Heart Chambers: Pulmonary Pump

• Right Atrium (forms most of base of heart)– Receives O2-poor blood from body via IVC, SVC, Coronary sinus

– Ventral wall (w/Pectinate muscles) and dorsal wall (no pectinate muscles) separated by crista terminalis

– Fossa Ovalis- on interatrial septum, remnant of Foramen Ovale

• Right Ventricle– Receives O2-poor blood from right atrium through tricuspid valve

– Pumps blood to lungs via Pulmonary Semilunar Valve in pulmonary trunk

– Trabeculae Carnae- muscle ridges along ventral surface

– Chordae Tendinae-fibrous cords running between AV valve cusps and papilary muscles

– Papillary Muscles (3)-cone-shaped muscles within ventricles to which chordae tendinae are anchored

– Moderator Band (septomarginal trabeucla)-muscular band connecting anterior papillary muscle to interventricular septum

pg 163, 165

Left Heart Chambers: Systemic Pump

• Left Atrium– Receives O2-rich blood from 4 Pulmonary Veins

– Pectinate Muscles line only auricle

• Left Ventricle (forms apex of heart)– Receives blood from Left Atrium via bicuspid valve– Pumps blood into aorta via Aortic Semilunar Valve to

body– Same structures as Rt Ventricle: Trabeculae carnae,

Papillary muscles (2), Chordae tendinae– No Moderator band

Heart Valves: Lub*-Dub**• *Tricuspid Valve: Right AV valve

– 3 Cusps (flaps) made of endocardium and CT– Cusps anchored in Rt. Ventricle by Chordae Tendinae– Chordae Tendinae prevent inversion of cusps into atrium– Flow of blood pushes cusps open– When ventricle is in diastole (relaxed), cusps hang limp in

ventricle– Ventricular contraction increases pressure and forces cusps closed

• *Bicuspid (Mitral) Valve: Left AV valve– 2 cusps anchored in Left Ventricle by chordae tendinae– Functions same as Rt. AV valve

• They close together pg 165

Semilunar Valves (the dub)

• Semilunar valves: prevents backflow in large arteries

• Pulmonary Semilunar Valve – Right Ventricle and Pulmonary Trunk

• Aortic Semilunar Valve– Left Ventricle and Aorta

• Made of 3 Cusps– As blood rushes past the cusps are flattened– As it settles they’re pushed down (valve closed)

pg 165

Flow of Blood• O2-poor blood (S+I VC, Coronary Sinus) enters Rt Atrium

• Travels through Tricuspid Valve into Rt Ventricle• Pumped out through Pulmonary Semilunar Valve into

Pulmonary trunk (branches into Pulmonary Arteries) and to lungs

• After circulating through lungs, O2-rich blood returns to the heart through 4 Pulmonary veins

• The O2-rich blood enters the Left Atrium

• Travels through Bicuspid/Mitral Valve into Left Ventricle• Pumped out through Aortic Semilunar Valve into Aorta to

be distributed to rest of body by descending aorta and branches of aortic arch

Cardiovascular Flow of Blood

• HeartArteries(conducting-distributing) ArteriolesCapillaries of tissues

• At Capillaries O2 is delivered and CO2

picked up

• CapillariesVenulesVeinsHeart

Circuits

• Pulmonary Circuit– Vessels carrying blood to and from lungs– Pulmonary arteries and veins

• Systemic Circuit– Vessels carrying blood to and from the rest of

the body– All other vessels

Blood Flow to Supply the Heart Muscle • Heart wall too thick for diffusion of nutrients

• Rt and Lft Coronary Arteries– Branch from Ascending Aorta

– Have multiple branches along heart

– Sit in Coronary Sulcus

– Coronary Heart Disease

• Cardiac Veins– Coronary Sinus (largest)

– Many branches feed into sinus

– Sits in Coronary Sulcus

pg 171

Blood Vessels

• Powered by the heart!• Carry blood to and from the heart• 3 main types:

– Arteries• Carry blood away from heart• arterioles

– Capillaries– Veins

• Carry blood toward heart• Venules

Anatomy of Arteries and Veins• Tunica externa

– Outermost layer– CT w/elastin and collagen– Protects, Strengthens, Anchors

• Tunica media– Middle layer– Circular Smooth Muscle– Collagen & Elastic Fibers– Vaso-constriction/dilation

• Tunica intima– Innermost layer– Endothelium– Minimize friction

• Lumen

Vessels of Cardiovascular System:Arteries

• Carry blood AWAY from heart

• Systemic Circuit: carry O2 blood

• Pulmonary Circuit: carry de-O2 blood

• Walls thicker than Veins– Tunica media > Tunica externa

• 3 Types– Conducting (elastic)

• large, elastin, high pressure

– Distributing (muscular)• medium size, to organs

– Arterioles• smallest

Capillaries• Smallest BV• Usually 1 RBC thick• 1 layer endothelial cell thick surrounded by basal lamina• Deliver O2 and nutrients to cells and remove waste• Capillary Beds: networks of capillaries

– Regulating amount of blood going to cells throughout tissues– Supply tissues and organs that otherwise have poor capillary circulation

• Epithelium, cartilage has no capillaries

Vessels of Cardiovascular System:Veins

• Carry blood from capillaries INTO the heart• Systemic Circuit: O2 poor blood• Pulmonary Circuit: O2 –rich blood• Pressure in Veins less than that in arteries

– Thinner walls than arteries (tunica externa > tunica media, less elastin)

– Larger lumen than arteries– Contain valves (made of T. intima)– Normal movement, Muscular contraction push blood through

• Venules- smallest veins

Cardiovascular Blood Flow• Portal System: Special vascular circulation where

blood goes through 2 capillary beds before returning to the heart to achieve 2nd function– (eg) Hepatic Portal System: aids digestion by picking up

digestive nutrients from stomach + intestines and delivers to liver for processing/storage

– Pick-up occurs at capillaries of stomach and intestine– Via Hepatic Portal Vein goes to capillaries of liver– Via Hepatic Vein blood goes back to heart

Vascular Anastomoses• Vessels unite and connect• Arteriole Anastomoses

– Communication between arteries

– Joints, Abdominal Organs, Brain, Heart

• Venous Anastomoses– Communication between veins

– More common

– (eg) back of hand

• Vaso Vasorum– Tiny arteries, veins, capillaries in tunica externa of vessels to

nourish them (outer half)

pg 726

Fetal Circulation

• All major vessels in place by third month• 2 main differences:

– 1. Fetus must supply blood to placenta

– 2. Lungs do not need much blood because respiratory organ is the placenta

1. Blood to Placenta• Umbilical vessels

– Run in umbilical cord– 2 umbilical arteries

• Carry blood (little oxygen and waste) to placenta

– 1 umbilical vein• Returns this blood (with oxygen and nutrients) to fetus and to portal vein (to

liver)

• Ductus venosus– Shunt that puts blood to hepatic veins, IVC, and RA from placenta– Too much blood for liver to handle– Results in highly O2 blood going to heart

2. Bypassing the Lungs:Foramen Ovale

• Becomes Fossa Ovalis• Hole in the inter-atrial septum• Allows blood to flow from RA to LA• Bypasses the RV

– Would usually bring blood to lungs

pg 163

2. Bypassing the Lungs: Ductus Arteriosus

• Becomes Ligamentum arteriosum• Carries blood from pulmonary trunk to aortic arch

– Empties distal to coronary arteries• This enables the heart and brain to receive the most highly

oxygenated blood

• Bypasses the lungs

pg 186

First Breath!!

• Lungs inflate– Ductus arteriosus constricts and closes

• Oxygenated blood begins pouring into LA for first time– Raises the pressure within the LA– This pushes the 2 flaps of foramen ovale

together and closes it