The Heart and Circulation - ECC-BOOK - Extracorporeal Circulation ...

The Heart and Circulation
Cardiovascular System = Heart, Blood and Vessels
Lymphatic System = Lymph nodes, Organs and Vessels

The Heart
• External Innervation
– Vagus (parasympathetic)
– C + T sympathetic chain ganglion
• 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 524

• Oblique Position
Location of Heart in Chest
• 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

Location of Heart in Thorax
pg 523

pg 555
External Features of Heart
• Interventricular sulcus
• Coronal/Coronary sulcus
• Auricles of atria
• Apex
• Base
• Coronary vessels
• Ligamentum Arteriosum

Pg 555, 554
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

• Epicardium (most superficial)
– Visceral pleura
• Myocardium (middle layer)
– Cardiac muscle
– Contracts
• Endocardium (inner)
– Endothelium on CT
– Lines the heart
– Creates the valves
Layers of
Heart
pg 524

Right Heart Chambers: Pulmonary Circuit
• Right Atrium (forms most of base of heart)
– Receives O 2 -poor blood from body via IVC, SVC, Coronary sinus
– Ventral wall = rough Pectinate muscle
– Fossa Ovalis- on interatrial septum, remnant of Foramen Ovale
• Right Ventricle
– Receives O 2 -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
– Papillary Muscle-cone-shaped muscle to which chordae tendinae
are anchored
– Moderator Band-muscular band connecting anterior papillary
muscle to interventricular septum

Left Heart Chambers: Systemic Circuit
• Left Atrium
– Receives O 2 -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, Chordae tendinae
– No Moderator Band

Chambers of Heart

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
• **Semilunar valves: prevents backflow in large arteries
– Pulmonary Semilunar Valve: Right Ventricle and Pulmonary Trunk
– Aortic Semilunar Valve: Left Ventricle and Aorta
– 3 cusps: blood rushes past they’re flattened, as it settles they’re pushed down
(valve closed)

Heart Valves
pg 527

Flow of Blood
Pulmonary Circuit
• O 2-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, O 2 -rich blood returns to the heart
through 4 Pulmonary veins
Systemic Circuit
• The O 2 -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 Circuits
pg 522

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

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
pg 546

Vessels of Cardiovascular System:
Arteries
• Carry blood AWAY from heart
• Systemic Circuit: carry O 2 blood
• Pulmonary Circuit: carry de-O 2 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

Vessels of Cardiovascular System:
• Smallest blood vessels
Capillaries
• Single layer of endothelium surrounded by basal lamina
• Deliver O 2 and nutrients to cells and remove waste
• Capillary Beds: networks of caps. Regulating amount of
blood going to cells throughout tissues
• Tendons, Ligaments poorly vascularized
• Epithelium, cartilage has no capillaries

Vessels of Cardiovascular System:
Veins
• Carry blood from capillaries INTO the heart
• Systemic Circuit: O 2 poor blood
• Pulmonary Circuit: O 2 –rich blood
• 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

Movement through Veins
pg 551

Cardiovascular Blood Flow
• HeartArteries(conducting-distributing)
ArteriolesCapillaries of tissues
• At Capillaries O 2 is delivered and CO 2 picked up
• CapillariesVenulesVeinsHeart
• Portal System: Special vascular circulation where blood goes
through 2 capillary beds before returning to the heart to
achieve 2 nd 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

Hepatic Portal System
pg 570

pg 568
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)

Fetal Circulation: 2 main differences
• All major vessels are in place by 3 rd month
• Blood flows in same direction as in adults
1) Fetus must transport blood
to and from the placenta
2) Lungs are not functional,
and do not need much
blood

Fetal Circulation: Blood to Placenta
• Fetus must supply placenta w/blood
• Umbilical Vessels: carries blood to/from placenta
– 2 Umbilical Arteries = bring blood that contains waste &
little O 2 from fetus to placenta
– 1 Umbilical Vein = brings blood w/O 2 and nutrients to
fetus from placenta (some goes to portal vein to process in
liver)
• Ductus Venosus = shunt taking blood returning from
placenta to fetus directly to heart, largely bypassing
liver
– Too much blood for liver to handle
– Results in highly O 2 blood going to heart

Fetal Circulation: Bypassing the Lungs
• Fetal Lungs are not functional and do not need large
amounts of blood
• Foramen Ovale (becomes Fossa Ovalis)
– Small hole in inter-atrial septum allows blood to flow
directly from Rt. Atrium to Lft. Atrium
– This largely bypasses the Rt. VentriclePulmonary trunk
that would bring blood to lungs
• Ductus Arteriosus (becomes Ligamentum Arteriosum)
– Shunt directs blood from Pulmonary Trunk to Aortic arch,
largely bypassing lungs

Pg 106
Bypassing the Lungs

Remnants of Fetal Circulation
• Ligamentum teres = Round ligament
– Remnant of the umbilical vein
– Anterior abdominal wall
• Ligamentum venosum
– Remnant of ductus venosum
– On liver’s inferior surface
• Medial Umbilical Ligaments
– Remnant of umbilical arteries
– Anterior abdominal wall below navel
– Also gives branch to urinary bladder

The Lymphatic System
• Function: to collect excess tissue fluid collecting at
arteriole end of capillary beds, and return leaked blood
proteins to blood (maintain osmotic pressure needed to
take up water into bloodstream)
• Lymph is moved through vessels
– Pulse of nearby arteries
– Contraction of surrounding skeletal muscle
– Regular movement of body (wiggling legs)
– Muscle in Tunica Media
• Lacteals-lymphatic capillaries w/unique function
– In mucosa of small intestine, receive digested fat from intestine
– Fatty lymph becomes milky = Chyle
– Chyle goes to bloodstream

Lymphatic System…The Players:
• Lymph- clear fluid from loose CT at capillaries
• Lymphatic capillaries (near blood capillaries)
• Lymph collecting vessels (small, 3 tunicas, # valves)
• Lymph nodes (sit along collecting vessels)-clean
lymph of pathogens, they are NOT glands
• Lymphatic trunks (convergence large collecting
vessels)
– Lumbar, intestinal, bronchomediastinal, subclavian, jugular
• Lymphatic ducts empty into veins of neck