Download ventricles.

Missing Notes: Unit Four
Hello Class,
I’m hoping to cover some of what’s here in class on
Wednesday. See you soon,
Julian
Regions within the Mediastinum
Superior
Anterior
Posterior
Middle
Lungs – External anatomy
 Each lung is conical and has a base and an
apex.
 The costal surface contacts the ribs and the
concave mediastinal surface faces the
mediastinum.
 The mediastinal surface contains the hilum,
where bronchi, blood vessels, nerves and
lymphatic vessels connect with the lung.
Lungs
 Each lung has a cardiac impression (larger on
the left).
 Each lung has an oblique fissure that divides
the lung into superior and inferior lobes. The
right lung also has a horizontal fissure and a
middle lobe.
 The lingula of the left lung is homologous with
the middle lobe of the right lung.
 Major vessels also make impressions, like the
aortic impression of the left lung.
External Heart Anatomy

Composed of four chambers: two smaller and
superior atria and the two larger and inferior
ventricles.
An ear-shaped anterior extension of each atrium
is its auricle.
 The atria and ventricles are separated from each
other by a groove called the coronary sulcus
 The anterior interventricular sulcus and
posterior interventricular sulcus are grooves
between the ventricles and run from the
coronary sulcus toward the heart’s apex.
Internally, the interventricular septum follows
this line.

Conducting System of the Heart

The electrical impulse that initiates the
heartbeat comes from a group of
specialized cardiac muscle cells called the
sinoatrial (SA) node.

The SA node generates 70-80 impulses
per minute under parasympathetic control.
Conducting System of the Heart
Impulses from the SA node travel to the left
atrium and the atrioventricular (AV) node
located in the floor of the right atrium.
 Electrical impulses pass into the
atrioventricular bundle (bundle of His) which
extends into the interventricular septum and
branches into left and right bundles.
 These bundles conduct the impulse to cells
called Purkinje fibers that spread the impulse
superiorly from the apex to all of the ventricular
myocardium.

Conducting System of the Heart
Sequence of Heart Chamber
Contractions
1.
2.
3.
4.
SA node generates an impulse
Both atria contract almost simultaneously
(systole) while ventricles are relaxing
(diastole)
Impulse goes to AV node and then to the
ventricles
Ventricles contract (systole) while atria
relax (diastole).
Innervation of the Heart
The heart, like most internal organs, is
innervated by the sympathetic and
parasympathetic divisions of the autonomic
nervous system.
 The anatomical components of both divisions
make up the coronary plexus.
 Sympathetic innervation of the heart is supplied
by fibers from the sympathetic trunks. This
input increases the rate and force of heart

contractions.

Parasympathetic innervation is supplied by
branches of the Vagus N (CN X) and decreases
heart rate.
External Heart Anatomy
External Heart Anatomy
Right Atrium
Three veins carry low-oxygen blood into the R atrium:
1. Coronary sinus
2. Superior vena cava
3. Inferior vena cava
The right atrioventricular valve separates the
atrium from the ventricle.
On the wall of the right atrium are myocardial features
called pectinate muscles. These ‘muscles’ stop
on a smooth band called the crista terminalis.
The interatrial septum is the wall between the atria.
The fossa ovalis is a remnant of a fetal opening
here called the foramen ovale.
The Ventricles
The interventricular septum forms a thick
wall between the ventricles.
 The inner wall of the ventricles display
myocardial features called trabeculae

carneae.
The cusps of the A/V valves are secured to the
myocardium via papillary muscles and
Chordae tendineae.
 In the right ventricle is the septomarginal
trabecula (moderator band) which secures a
large papillary muscle to the interventricular
septum.
 The right ventricle has a smooth cone-shaped
upper portion called the conus arteriosus
which leads to the pulmonary semilunar valve.

Right Ventricle
Left Atrium
This chamber receives high-oxygen blood
from the lungs through the pulmonary
veins.
 The left atrium is separated from the left
ventricle by the left atrioventricular
valve which is also referred to as the
bicuspid or mitral valve.

The Thoracic Duct
 The thoracic duct is the largest lymphatic vessel
 Like all lymphatic vessels, it transports interstitial
fluid (lymph) into the bloodstream.
 The thoracic duct collects lymph from ~3/4 of the
body.
 The thoracic duct drains into the junction between
the left subclavian and internal jugular veins.
5. Lymphatic Ducts