CIRCULATORY ANATOMY
HEART WALL STRUCTURE
I. Endocardium: epithelial lining of heart
chambers in contact with blood.
II. Myocardium: cardiac muscle and connective tissue fibers of heart wall; responsible for creating pressure changes which
move blood.
III. Epicardium or Visceral Percardium: outer
layer of heart wall.
IV. Pericardial Sac: thick connective tissue,
fluid filled sac surrounding heart lined by
parietal pericardium (opposite visceral
pericardium).
SHARK HEART
I. Heart Chambers
A. Atrium: large, thin-walled, singlechambered sac between sinus venosus
and ventricle.
B. Ventricle: thick-walled single-chambered sac on most ventral side of
heart; extends anteriorly to muscular
conus arteriosus.
C. Sinus Venosus: triangular sac seen by
lifting posterior end of ventricle.
II. Apertures and Valves
A. Sinoatrial Aperture: opening between
sinus venosus and atrium; guarded by
sinoatrial valve.
B. Atrioventricular Aperture: opening
between atrium and ventricle; guarded
by atrioventricular valve.
C. Semilunar Valves: pocket-like valves
located along wall of conus arteriosus.
SHEEP HEART
I. External Features
A. Atrioventricular Groove (or Sulcus):
deep depression separating (upper)
atria from (lower) ventricles
B. Anterior Interventricular Sulcus:
diagonal indentation across anterior
side of the ventricles; can be used to
distinguish right from left ventricles.
C. Posterior Interventricular Sulcus: an
indentation going perpendicular to
atrioventricular groove on posterior
side of ventricles; can be used to
distinguish right from left ventricles.
II. Heart Chambers: two, relatively small, atria
on superior side of heart; two, relatively
large, ventricles on inferior side of heart.
A. Right Atrium: deoxygenated blood
enters heart to this chamber from:
1. coronary sinus
2. superior vena cava
3. inferior vena cava
B. Right Ventricle: receives blood from
right atrium; pumps blood into pulmonary trunk and onto lungs.
C. Left Atrium: oxygenated blood enters
heart into this chamber from four pulmonary veins.
D. Left Ventricle: receives blood from
left atrium; pumps blood into aorta
and onto body; separated from the
right ventricle by interventricular
septum.
IV. Valves: flaps of connective tissue covered
by endothelium; act to close off ventricles
and insure one way blood flow.
A. Atrioventricular Valves: separate atria
from ventricles
1. Tricuspid Valve: made up of three
flaps; found on right side of heart
2. Bicuspid (or Mitral) Valve: made
up of two flaps; found on left side
of heart.
B. Semilunar Valves: separate ventricles
from blood vessels that they pump to.
1. Pulmonary Semilunar Valve:
found at entrance of pulmonary
trunk.
2. Aortic Semilunar Valves: found at
entrance of aorta
42
V. Blood Vessels Associated with Heart
A. Superior and Inferior Vena Cava:
largest veins that deliver deoxygenated blood from head and upper extremity and trunk and lower extremity,
respectively.
B. Pulmonary Trunk (or Artery):
transports deoxygenated blood from
right ventricle to lungs.
C. Pulmonary Veins: four vessels that
carry freshly oxygenated blood from
lungs to left atrium.
D. Aorta: largest artery of body; carries
oxygenated blood from left ventricles
to body.
E. Coronary Arteries: first two branches
of aorta; supplies heart wall with
oxygenated blood.
F. Coronary Sinus: large diameter vein
that drains blood from heart wall into
right atrium.
BLOOD VESSELS
Named blood vessels are of two types:
arteries and veins. The major functional difference between them is the direction of blood
flow. Arteries carry blood away from the heart
while veins carry blood to the heart – regardless of whether that blood is oxygenated or
deoxygenated.
Blood vessels change names for one of two
basic reasons. The blood vessel may be one
continuous tube but its name is changed as it
passes into a different body region. The second
reason is that an artery will bifurcate (branch)
and each branch will have a different name
while the original artery has ended; for veins
two veins will merge to form a ‘new’ third
vein.
In the general circulation, blood travels
from an artery, into capillaries, then into a vein
before it returns to the heart. However, blood
in a portal system travels from an artery into
capillaries, into a vein (or veins), into a second
set of capillaries and finally into a vein before
returning to the heart.
SHARK
I. Arterial System
A. Ventral Aorta: a single forward continuation of the conus arteriosus; carries
deoxygenated blood.
B. Afferent Branchial Arteries: three
primary pairs arise from ventral aorta;
posterior pair arises near conus arteriosus and bifurcates near its origins;
next pair remains undivided; anterior
pair is terminus of ventral aorta and
bifurcates in gill region; these are
numbered 1 to 5, anterior to posterior
direction; carry deoxygenated blood to
gills.
C. Efferent Branchial Arteries: four pairs
of arteries (1 to 4), extending posteromedially; formed by merging of an artery from an anterior side of gill slit
and one from posterior side of gill slit;
carry oxygenated blood from gills to
single, midline dorsal aorta.
D. Esophageal Arteries: arise from
second efferent branchial artery; runs
posteriorly; carries oxygenated blood
to dorsal pharynx and esophagus.
E. Radices Aortae (singular = radix aorta):
arise from first branchial artery, extending forward.
F. Subclavian Arteries: arise from each
side of dorsal aorta between third and
fourth efferent branchial arteries;
curve laterally toward pectoral fins
giving off several branches to supply
oxygenated blood to lateral and anterior body wall and pectoral fin.
G. Dorsal Aorta: large single midline
artery formed by convergence of efferent branchial arteries; enters pleuroperitoneal cavity, giving off paired
and unpaired abdominal branches.
H. Celiac Artery: single artery arising
from dorsal aorta; its branches supply
oxygenated blood to gonads, esophagus and cardiac end of stomach; bifurcates into gastrohepatic and pancreaticomesenteric arteries.
J. Genital Arteries: arise from celiac
43
artery to supply gonad.
K. Gastrohepatic Artery: divides almost
immediately into gastric artery, supplying blood to stomach; and hepatic
artery, which curves sharply upward
and supplies liver.
L. Pancreaticomesenteric Artery: supplies
oxygenated blood to pylorus, pancreas
and intestine; runs caudally behind pylorus and continues to anterior intestinal wall where, after giving off several branches, becomes anterior intestinal artery.
M. Posterior Intestinal Artery: arises from
dorsal aorta; supplies intestine.
N. Gastroplenic Artery: arises from dorsal aorta passing to spleen and onto
stomach.
O. Iliac Arteries: arises from dorsal aorta,
emerging from behind kidneys; supplies pelvic fins; branches arise to
supply ventral body wall.
P. Caudal Artery: continuation of dorsal
aorta to supply tail; travels through
hemal arch.
II. Systemic Venous System
A. Hepatic Veins: drain blood from
hepatic sinuses into sinus venosus.
B. Common Cardinal Veins: enters lateral
corner of sinus venosus; collects deoxygenated blood from anterior cardinal veins, posterior cardinal veins
and subclavian veins.
C. Anterior Cardinal Veins: drain sides of
head.
D. Posterior Cardinal Veins: lie immediately lateral to dorsal aorta and medial
to each kidney; drain blood into two
large lateral posterior cardinal sinuses
(these are confluent across midline);
receives blood from kidneys, genitals,
and body wall.
E. Subclavian Veins: receives blood from
cloacal area, pelvic fins, abdominal
wall and pectoral fins.
III. Hepatic Portal System: begins in capil-
laries of digestive wall which converge to
larger veins and terminates in capillaries of
liver which then drain through hepatic
vein.
A. Hepatic Portal Vein: broad channel
extending into right lobe of liver; receives blood from three tributaries:
gastric, pancreaticomesenteric and
lienomesenteric veins.
B. Gastric Vein: most anterior tributary;
drains blood from stomach.
C. Pancreaticomesenteric Vein: drains
blood from right side of intestine and
spleen.
D. Lienomesenteric Vein: middle tributary which receives blood from left
side of interstine and posterior spleen.
IV. Renal Portal System: begins in capillaries
of tail and terminates in renal capillaries;
systemic veins then drain blood from these
capillaries.
A. Renal Portal Veins: travel cranially
along lateral margins of kidneys;
receive blood from caudal vein.
CAT
I. Arterial System
A. Aorta: begins at base of left ventricle
moving cranially for a short distance
and curves to the left as arch of the
aorta then moving posterior to heart at
thoracic aorta; it pierces diaphragm to
become abdominal aorta; all system
blood travels through aorta.
B. Brachiocephalic Artery: first branch of
aortic arch; ascends cranially giving
off left common carotid artery; bifurcates into right common carotid artery
and right subclavian artery.
C. Common Carotid Arteries: found on
lateral margin of trachea; at base of
skull bifurcates in to internal carotid
arteries, which supplies brain; and
external carotid arteries, which, with
its branches supplies structures on
external side of skull.
D. Left Subclavian Artery: second branch
44
of aortic arch; ascends cranially curving to left toward left forelimb; has
two branches (this is also true of right
subclavian artery):
1. Internal Mammary Arteries: passes
caudoventrally to internal surface
of sternum; supplies pericardium
and diaphragm.
2. Vertebral Arteries: passes dorsally
to enter transverse foramina of
cervical vertebrae; supplies brain.
3. Axillary Arteries: arises as subclavian arteries pass through thoracic wall; continues to arm as
brachial artery, which then bifurcates into radial and ulnar
arteries; these all supply arm and
forearm muscles.
E. Thoracic Aorta: gives rise to intercostals arteries (thoracic wall), bronchial
arteries (lungs), and esophageal
arteries (esophagus).
F. Celiac Trunk: first branch of abdominal aorta; short vessel divides into three
large branches:
1. Hepatic Artery: passes deep to
stomach; supplies liver, and parts
of gut.
2. Left Gastric Artery: runs ventral to
lesser curvature of stomach to
supply this organ.
3. Splenic Artery: largest of three
branches; divides into two large
branches, both supplying spleen.
G. Superior Mesenteric Artery: second
branch of abdominal aorta; travels
caudoventrally, passing under colon;
supplies cranial two-thirds of large
and small intestine.
H. Adrenolumbar Arteries: paired blood
vessels traveling laterally to supply
adrenal glands, diaphragm and adjacent musculature.
J. Renal Arteries: arise at same level to
supply kidneys.
K. Genital Arteries: arise at same level; in
male travel caudally to testes; in
females travel laterally to ovaries.
L. Inferior Mesenteric Artery: arise at
level of last lumbar vertebra, passing
to large interstine; supplies caudal
one-third of large and small intestine.
M. Lumbar Arteries: series of seven
paired vessels arising from posterior
side of abdominal aorta; supplies spine
and back muscles.
N. External Iliac Arteries: two terminal
branches of abdominal aorta that
travel an oblique caudal course to exit
abdominal wall where it become femoral arteries; by way of its branches,
deep femoral arteries, the bladder,
ventral body wall and testes are
supplied.
O. Internal Iliac Arteries: run parallel to
external iliac arteries, but remain within pelvic cavity where it supplies
bladder, rectum and pelvic muscles.
II. Venous System
A. Superior Vena Cava: major vein that
receives blood from head, thorax and
forelimbs; drains directly into right
atrium; forms by union of brachiocephalic veins.
B. Azygos Vein: single vein lying on
right side of spinal column; drains
blood from dorsal abdominal wall;
drains directly into superior vena cava.
C. Internal Mammary Veins: drains ventral abdominal and thoracic walls into
superior vena cava.
D. Brachiocephalic Veins: formed by
union of subclavian and external jugular veins; also receives blood from
vertebral veins.
E. Subclavian Veins: continuation of
axillary veins which are continuations
of brachial veins; these drain blood
from forelimb.
F. External Jugular Veins: pass obliquely
across sternomastoid muscles to cranial end of manubrium; receive internal
jugular veins; both jugular veins drain
blood from head.
G. Inferior Vena Cava: major vein that
receives blood from abdominal organs, trunk muscles and hindlimbs;
45
drains directly into right atrium formed by union of common iliac veins.
H. Common Iliac Veins: formed by union
of large external iliac veins, continuations of femoral veins; and smaller internal iliac veins; these receive blood
from hind limb and pelvis.
J. – L. The following abdominal veins are
found alongside their corresponding
arteries:
J. Adrenal Veins
K. Renal Veins
L. Genital Veins
Note that left adrenal and left genital
veins drain into left renal vein while
right adrenal and right genital drain
directly into inferior vena cava.
III. Hepatic Portal System: begins in capillaries of digestive wall which converge to
larger veins and terminates in capillaries of
liver which then drain through hepatic
veins into inferior vena cava.
A. Hepatic Portal Vein: large vein carrying deoxygenated blood to liver;
receives blood from two tributaries:
gastrosplenic and superior mesenteric
veins.
B. Gastrosplenic Vein: drains blood from
stomach and spleen.
C. Superior Mesenteric Vein: drains
blood from intestines through several
tributaries.
46