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
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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
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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
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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)
pg 163, 165
– 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
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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
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
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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
• HeartArteries(conducting-distributing)
ArteriolesCapillaries of tissues
• At Capillaries O2 is delivered and CO2
picked up
• CapillariesVenulesVeinsHeart
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
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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
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Middle layer
Circular Smooth Muscle
Collagen & Elastic Fibers
Vaso-constriction/dilation
• Tunica intima
– Innermost layer
– Endothelium
– Minimize friction
• Lumen
Vessels of Cardiovascular System:
Arteries
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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
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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
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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
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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