Download Circulatory System Part 3

17
BLOOD VESSELS
Blood Vessels (dynamic structures that pulsate, as well as constrict and relax)
1. Main types of Vessels
 Arteries – vessels through which blood is pumped away from the heart.
Arteries branch into arterioles and finally into capillary beds that feed the
tissues
 From the capillary beds, blood is pumped into venules that empty into large
veins (which take blood back to the heart through the great veins).
 Gas and nutrient exchange occurs only through the capillary walls
 60,000 miles of vessels in a human
2. All vessels except capillaries have 3 layers or tunics
a) Tunica Interna or Tunica Intima -(inner most layer) continuous with lining of
heart; reduce friction of blood through lumen (the inside of the vessels)
b) Tunica Media – Composed of smooth muscles and sheets of elastin – allows
muscles to stretch and maintains blood pressure and continuous blood circulation
i. Vasoconstriction – tighten (decreases diameter of lumen) triggered by
low Oxygen in Systemic Circuit and cold temperatures
18
Vasodilation – open, loosen (increases diameter of lumen) triggered by
excess or adequate Oxygen in Systemic Circuit and warm temperatures
c) Tunica Externa – Composed of collagen fibers
i. Protect and reinforce vessel
ii. Anchor to surrounding structures
iii. Contains nerve fibers and lymphatic vessels
ii.
3. Capillaries – only vessels to directly serve cells in tissues; give cells oxygen (also
hormones and nutrients) and remove carbon dioxide (and other wastes)
a) Thin wall of just inner layer = Tunica Interna
b) 3 types of Capillaries
i. Continuous capillaries– abundant in the skin and muscles
 Uninterrupted lining
 Intercellular clefts allow fluids and small solutes through
ii.
Fenestrated capillaries – (fenestra = windows) abundant in small
intestine, kidneys, endocrine glands – allows slightly larger things to pass
through
 Endothelial cells (lining) have oval pores called fenestra
19
iii.
Sinusoids capillaries – leaky capillaries abundant in the liver, bone
marrow, lymphoid tissues and some endocrine
 Also have Fenestrations – larger holes
 Large intercellular clefts – leaky; lymphoid tissues and large lumens
c) Capillary beds – capillaries function as networks, not independently
i. Microcirculation – blood flow from arterioles  capillary bed  venules
ii. Precapillary sphincter – contracted = closed = blood will bypass tissue
when blood is not needed there (e.g., muscles tissue does not need a lot of
blood when at rest)
20
LYMPHATIC SYSTEM
Lymphatic System – pumpless system of vessels, lymph nodes, and other lymphoidal organs
that aides the cardiovascular system in its function
21
Lymphatic Vessels – function to pick up the excess tissue fluid (lymph – primarily water and
some dissolved proteins) that has leaked from the blood and return it to the bloodstream
Although the lymphatic system is a low pressure pumpless system, the transport of lymph is
actually conducted by smooth muscles in the lymphatic vessel walls. Small valves keep the
lymph toward the heart during these contractions.
Edema – accumulation of fluid in the body
tissues
Right Lymphatic Duct – drains the lymph
from the right arm right side of the head and
thorax and empties into the Subclavian Vein
Thoracic Duct – drains lymph from the rest of
the body and empties into the Subclavian Vein
22
Lymph Nodes – closely
related to the immune system
the lymph nodes are
responsible for removing
foreign material (bacteria and
tumor cells) from the
lymphatic system by producing
lymphocytes. Particularly
large clusters of lymph nodes
are found in the inguinal,
axillary, and cervical regions.
Macrophages – cells of lymph
nodes that engulf/destroy
bacteria, viruses, & foreign
substances
Lymphocytes – a type of
White Blood Cell (which arise
from Red Bone Marrow) also found in the lymph nodes respond to foreign bodies as well
Other Lymphoidal Organs include the spleen, thymus gland, tonsils, and Peyer’s Patches of the
intestine as well as bits of lymphatic tissue scattered in the epithelial and connective tissues.
Spleen – blood rich organ that filters & cleanses blood (rather than lymph as lymph nodes do)
Functions of the Spleen:
 Destroys worn-out RBCs and returns some of their breakdown products to the liver
 Synthesizes lymphocytes
 Stores Platelets
 Blood Reservoir
Thymus Gland – a lymphatic mass found low in the throat overlying the heart that produces
hormones that function in programming of lymphocytes to carry out certain functions in the body
23
Tonsils – small masses of lymphatic tissue found in the throat
that trap and remove bacteria or other foreign pathogens
Peyer’s Patches – small masses of lymphatic tissue in the wall
of the small intestine that trap bacteria (always in high numbers
in intestine) and keep them from penetrating the intestinal wall
24
25
Major Arteries in Systemic Circulation
Arteries are typically located deep in well protected areas of the body.
Aorta – largest artery in the body
Major Regions and Branches of the Aorta:
1. Ascending aorta – first part of the aorta the ascends from the heart
a. Right and Left Coronary Arteries that serve the heart
2. Aortic Arch – large bend in the aorta soon after is leaves the heart
a. Brachiocephalic Artery – branches into the Right Common Carotid Artery and
Right Subclavian Artery
b. Left Common Carotid – branches into the Left Internal Carotid that serves the
brain and the Left External Carotid that serves the skin and muscles of the head
and neck
c. Left Subclavian Artery – branches into the Vertebral Artery (which serves part if
the brain) the Axillary Artery and the Brachial Artery. The Brachial Artery
further divides into the Radial and Ulnar Arteries.
3. Thoracic Aorta – next section of the aorta contained within the thorax running on the
anterior side of the spine
a. Intercostal Arteries (ten pairs) – supply the muscles of the thoracic wall
b. Bronchial Arteries – serve the lungs
c. Esophageal Arteries and Phrenic Arteries serve the esophagus and diaphragm
respectively
4. Abdominal Aorta – last section of the aorta located inferior to the diaphragm within the
abdominal cavity
a. Celiac Trunk – branches into the Left Gastric Artery (supplies the stomach), the
Splenic Artery (serves the spleen), and the Common Hepatic Artery (supplies the
liver).
b. Superior Mesenteric Artery – supplies the small intestines and first ½ of the large
intestine
c. Renal Arteries – serve the kidneys
d. Gonadal Arteries – serve the gonads (called the ovarian arteries in females and
testicular arteries in males)
e. Lumbar Arteries – several pairs of arteries serving the heavy muscles of the
abdominal and trunk walls
f. Inferior Mesenteric Artery – supplies second ½ of large intestine
g. Common Iliac Arteries – divide into the Internal Iliac Artery (supplies the bladder
and rectum) and the External Iliac Artery which enters the thigh and becomes the
Femoral Artery. The Femoral Artery and its branch the Deep Femoral Artery
which serve the thigh. At the knee the Femoral Artery Branches into the Popliteal
Artery which again splits into the Anterior and Posterior Tibial Arteries. The
Anterior Tibial Artery terminates into the Dorsalis Pedis Artery which supplies
the dorsum of the foot.
26
27
Major Veins in Systemic Circulation
Veins are typically located in more superficial areas of the body but some some follow the
course of the major arteries. With a few exceptions the naming of these veins is identical to that
of the companion arteries
Superior Vena Cava – veins draining the head and arms
Inferior Vena Cava – veins draining the lower body
Major Veins that drain into the Superior Vena Cava:
1) Radial and Ulnar Veins drain the forearm and unite to form the Brachial Vein which in
turn drains into the Axillary Vein
2) The Cephalic Vein which drains the lateral aspect of the arm also drains into the Axillary
Vein and the Basilic Vein that drains the medial aspect of the arm drains into the
Brachial Vein. The Cephalic and Basilic veins are joined at the anterior aspect of the
elbow by the median cubital vein.
3) The Axillary Vein and the External Jugular Vein (which drains blood from the skin and
muscles of the head) empty into the Subclavian Vein.
4) The Vertebral Vein drains the posterior part of the head as the Internal Jugular Vein
drains the dural sinuses of the brain.
5) The Brachiocephalic Veins receive blood from the Subclavian Vein, Vertebral Vein, and
Internal Jugular Veins before joining to form the Superior Vena Cava.
6) The Azygos Vein drains the thorax before leading into the Superior Vena Cava
Major Veins the drain into the Inferior Vena Cava:
1) The Anterior and Posterior Tibial Veins and Peronal Vein drain the leg before ascending
into the Popliteal Vein, then the Femoral Vein, and finally the External Iliac Vein.
2) The Great Saphenous Veins (the longest veins in the body) receive superficial drainage of
the leg beginning at the Dorsal Venous Arch and emptying into the Femoral Vein in the
thigh.
3) The Common Iliac Vein which is formed from the junction of the External Iliac Vein and
the Internal Iliac Vein drains directly into the Inferior Vena Cava
4) The Gonadal Veins drain the gonads and the Renal Veins drain the kidneys.
5) The Hepatic Portal Vein drains the digestive tract organs and carries this blood through
the liver before it enters the systemic circulation. The Hepatic Veins drain the liver.
28