Download ANPS 020 01-18

ANPS 020 Beneyto-Santonja 01/18/13
Blood Typing
 The surfaces of RBC are coated with glycoproteins and glycolipids, which are capable of
stimulating an immune response.
 These molecules (antigens) form the basis for the different blood groups
 A person with type A blood has type A antigens on their RBCs, but also has antibodies in their
plasma that will mount an attack on type B antigens if they are exposed to them.
 A person with type B blood has type B antigens on their RBCs, but also has antibodies in their
plasma that will mount an attack on type A antigens if they are exposed to them.
 A person with type AB blood has type A & type B antigens on their RBCs, but has no A or B
antibodies
 A person with type O blood has neither A nor B surface antigens on their RBCs, but have both A
and B antibodies
 Type O blood is considered the Universal donor  RBC can be given to any other blood type
without stimulating rejection (no surface antigens = nothing for new host to attack)
 Type AB individuals are considered the Universal recipients  they can receive blood of any type
without rejection (no A or B antibodies in host blood = no attack)
 “Rh” is another surface antigen important in blood typing; individuals are denoted Rh+ or Rhdepending on the presence or absence of this marker
Blood Typing: The issue with transfusions
 Transfusions of isolated RBC are usually given to replace someone’s RBC count and boost blood
volume.
 If RBC from someone with type B blood are given to someone with type A blood, the anti-B
antibodies in the recipient will violently attack the donated cells.
Blood Vessels: Anatomy
 To understand the construction of a blood vessel, let’s first review the important tissue types
involved
 Endothelium
o Recall that epithelial cells occur in sheets, with junctions (tight junctions and
desmosomes) tightly binding each cell to its neighbors.
o A simple squamous epithelium contains a single layer of flat cells; in blood vessels this
simple sqaumous epithelium is commonly called the endothelium
 Connective Tissue
o Connective tissue is usually located between layers and on the outside of organs,
including blood vessels.
 Smooth Muscle
o Smooth muscle is so named because it does not have visible striations in its cytoplasm. It
does contain actin and myosin, and contracts in the presence of calcium.
o When the smooth muscle layer contracts, the vessel diameter narrows (vasoconstriction).
o When the smooth muscle layer relaxes, the vessel diameter increases (vasodilation)
 Most blood vessels have a 3-layered wall (3 tunics)
o Tunica Intima: innermost
 Lined by the endothelium
 Supported by connective tissue (collagen)
o Tunica Media: middle layer
 Smooth muscle with various amounts of elastic fibers
o Tunica Externa: outer layer
 Connective tissue

Arteries have stronger, thicker walls than the vein of the same size; arteries generally contain more
smooth muscle and often more elastic fibers.
 Nerves innervate blood vessels, but are seldom seen in images as they are diffusely spread out
within the muscle layer
o These nerves are important for controlling blood vessel diameter
 Vessels can be categorized by size
o Large Vein, Medium-Sized Vein, Venule
o Elastic Artery, Muscular Artery, Arteriole
o Blood vessels closest to the heart have the largest diameter
o There is little smooth muscle in most veins
Vessels can be Categorized by Function
 Elastic Arteries: The largest arteries closest to the heart contain a lot of elastic fibers, and swell
with blood each time the heart pumps
 Muscular Arteries: smaller diameter arteries distributing to organs
 Capacitance Vessels: Because veins have little muscle and few elastic fibers in their wall, they
have little ability to resist stretch, and often hold much of the circulating blood
 Resistance Vessels: Arterioles are small in diameter with a few layers of smooth muscle;
contraction or relaxation of that muscle creates great changes in diameter, and thus great changes
in resistance to blood flow.
Distribution of Blood
 30-35% of blood volume contained in heart, arteries, and capillaries
 60-65% of blood in the venous system
Veins have valves to prevent blood from flowing backward
 Prevent blood from flowing backward in system
 Formed from foldings of tunica intima
 Compression of veins pushes blood toward heart
o “muscular pump” action of skeletal muscles around veins
Venous Valve Failure Allows Blood to Pool in Veins and Creates Distension in the Vein Walls
 Valve failure may be due to genetic factors or to locally high venous pressure
 Hemmorrhoids are distensions of anal veins
Blood Vessels: Anatomy of Capillaries
 A capillary is little more than a tube of endothelial cells supports by a basal lamina
 The thin wall allows exchange of materials (nutrients, wastes, oxygen, and carbon dioxide)
between the bloodstream and the tissues
 Capillaries are thus called the exchange vessels
 How substances pass through a capillary wall
o Transport through the epithelial cell membrane
 Diffusion (passive)
 Pinocytosis (active)
o Through pores or holes (fenestrations) in the epithelial cells
o Through spaces between epithelial cells
 There are 3 types of Capillaries based on the degree of “leakiness”
1. Continuous Capillaries
a. Have complete endothelial lining – cells tightly bound to one another
b. Are found in all tissues except epithelia and cartilage
c. Permit diffusion of water, small solutes, and lipid-soluble materials
d. Block blood cells and plasma proteins
e. Specialized continuous capillaries are found in the CNS and create the “bloodbrain barrier”
2. Fenestrated Capillaries
a. Have small pores in endothelial lining
b. Permit rapid exchange of water and larger solutes between plasma and
interstitial fluid
c. Found in areas requiring more exchange
i. Choroid plexus
ii. Endocrine Organs
iii. Kidneys
iv. Intestinal Tract
3. Sinusoidal Capillaries
a. Have large gaps between adjacent endothelial cells
b. Permit free exchange of water and large plasma proteins between blood and
interstitial fluid
c. Found in:
i. Liver, Spleen, Bone Marrow, Endocrine Organs
d. Phagocytic cells monitor blood at sinusoids
 Pre-capillary Sphincters
o Arterioles often have areas of extra muscle in their wall as they branch into a capillary
network; these sphincters contract to decrease blood flow into a capillary bed
Arteries and veins generally parallel to one another and share same names
The Systemic Arteries
 The single vessel leaving the left side of the heart is the Aorta
 Parts of the aorta include:
o The aortic arch
o The thoracic aorta (in the thoracic cavity)
o The abdominal aorta (below the diaphragm)
The Systemic Veins
 Blood returns to the right side of the heart through two large unpaired veins
 Above the diaphragm, blood returns through the superior vena cava
 Below the diaphragm, blood returns through the inferior vena cava
Pulmonary and Systemic Circulation Patterns
 General Functional Patterns
o Peripheral artery and vein distribution is the same on right and left (ie. Is symmetrical),
except near the heart
o The same vessel may have different names in different locations
o Tissues and organs usually have multiple arteries and veins; vessels may be
interconnected with anastomoses.