Human Anatomy chapter 14
Approximately ___ billion in number, capillaries form an extensive network of short (hundreds of μm in length), branched, interconnecting vessels that course among and make contact with the individual cells of the body.
20
he approximately _______ million arterioles have diameters that range in size from 15 μm to 30 μm. The wall thickness of arterioles is one-half of the total vessel diameter.
400
What do the walls of arterioles consist of?
Arterioles have a thin tunica interna with a thin internal elastic lamina containing small pores that disappear at the terminal end.
____________ ____________ are the largest arteries in the body, ranging from the garden hose-sized aorta and pulmonary trunk to the finger-sized branches of the aorta
Elastic arteries;They have the largest diameter among arteries, but their vessel walls (approximately one-tenth of the vessel's total diameter) are relatively thin compared to the overall size of the vessel.
What is the innermost layer of the tunica interna?
Endothelium, which is continuous with the endocardial lining of the heart.
What is the function of the endothelial cells?
It is now known that endothelial cells are active participants in a variety of vessel-related activities, including physical influences on blood flow, secretion of locally acting chemical mediators that influence the contractile state of the vessel's overlying smooth muscle, and assistance with capillary permeability.
Tissues with lower metabolic requirements, such as tendons and ligaments, contain more or less capillaries?
LESS;Capillaries are absent in a few tissues, such as all covering and lining epithelia, the cornea and lens of the eye, and cartilage.
Circumflex coronary artery feeds what side of the heart?
Left side
Body tissues with high metabolic requirements, such as muscles, the brain, the liver, the kidneys, and the nervous system, use more O2 and nutrients and thus have more or less extensive capillary networks?
MORE
These in turn merge to form progressively larger blood vessels called veins. __________ are the blood vessels that convey blood from the tissues back to the heart.
Veins
What is the function of venules?
Venules drain the capillary blood and begin the return flow of blood back toward the heart. And, They function as significant sites of exchange of nutrients and wastes and white blood cell emigration, and for this reason form part of the microcirculatory exchange unit along with the capillaries
What is the capillary bed?
a network of 10-100 capillaries that arises from a single metarteriole.
What is the endothelium?
a thin layer of flattened cells that lines the inner surface of the entire cardiovascular system (heart and blood vessels).
Because they carry blood toward the heart, veins are referred to as ________________ vessels
afferent
Anastomoses between arteries provide what?
alternative routes for blood to reach a tissue or organ
The wall of a blood vessel consists of three layers, or tunics, of different tissues which are?
an endothelial inner lining, a middle layer consisting of smooth muscle and elastic connective tissue, and a connective tissue outer covering.
Most tissues of the body receive blood from more than one artery. The union of the branches of two or more arteries supplying the same body region is called an ________________________
anastomosis
Elastic arteries include the two major trunks that exit the heart (the ____________ and the _____________________ trunk), along with the aorta's major branches, including the brachiocephalic, subclavian, common carotid, and common iliac arteries
aorta; pulmonary
What are the 5 main types of blood vesssels?
arteries, arterioles, capillaries, venules, and veins.
______________carry blood away from the heart to other organs.
arteries; artery= away
Literally meaning "small arteries," _________________ are abundant microscopic vessels that regulate the flow of blood into the capillary networks of the body's tissues
arterioles
Medium-sized arteries then divide into small arteries, which in turn divide into still smaller arteries called _________________
arterioles
pectinate muscle is with the ____________________.
atria
The second component of the tunica interna is a ______________ __________________deep to the endothelium
basement membrane
As the arterioles enter a tissue, they branch into numerous tiny vessels called _______________
capillaries
___________________, the smallest of blood vessels, have diameters of 5-10 μm, and form the "U-turns" that connect the arterial outflow to the venous return
capillaries
Exchange of materials occurs only through the walls of ____________________ and the beginning of ____________; the walls of arteries, arterioles, most venules, and veins present too thick a barrier.
capillaries; venules
The alternative route of blood flow to a body part through an anastomosis is known as ________________ __________________.
collateral circulation
Due to their plentiful elastic fibers, arteries normally have high _________________, which means that their walls stretch easily or expand without tearing in response to a small increase in pressure.
compliance
Because they conduct blood from the heart to medium-sized, more muscular arteries, elastic arteries also are called __________________ arteries.
conducting
Most capillaries are ______________ _______________, in which the plasma membranes of endothelial cells form a continuous tube that is interrupted only by intercellular clefts
continuous capillaries
The body contains three different types of capillaries what are they?
continuous capillaries, fenestrated capillaries, and sinusoids
the muscular arteries continue to branch and ultimately distribute blood to each of the various organs, they are called _________________ arteries.
distributing; Examples include the brachial artery in the arm and the radial artery in the forearm
Smooth muscle cells also produce the _____________ ___________ within the tunica media that allow the vessels to stretch and recoil under the applied pressure of the blood.
elastic fibers
These vessels are characterized by well-defined internal and external elastic laminae, along with a thick tunica media that is dominated by elastic fibers, the ______________ ________________
elastic lamellae
Veins lack the external or internal _____________ ____________ found in arteries
elastic laminae
Anastomoses may also occur between veins and between arterioles and venules. Arteries that do not anastomose are known as _____ arteries.
end
The thin walls of capillaries allow _____________ of substances between the blood and body tissues.
exchange
Because the primary function of capillaries is the exchange of substances between the blood and interstitial fluid, these thin-walled vessels are referred to as _________________ ______________.
exchange vessels
What is the primary role of the smooth muscle cells?
extend circularly around the lumen like a ring encircles your finger, is to regulate the diameter of the lumen wall.
The tunica ________ is often thicker than the tunica ___________ in muscular arteries.
externa;media
A less prominent network of elastic fibers, the _______________ ____________ _______________, forms the outer part of the tunica media and separates the tunica media from the outer tunica externa.
external elastic lamina
Where are fenestrated capillaries found?
found in the kidneys, villi of the small intestine, choroid plexuses of the ventricles in the brain, ciliary processes of the eyes, and most endocrine glands.
What is the sequence of blood from the heart in vessels?
from the heart and then in sequence through arteries, arterioles, capillaries, venules, and veins and then back to the heart.
What are intercellular clefts?
gaps between neighboring endothelial cells
What are fenestrated capillaries?
he plasma membranes of the endothelial cells in these capillaries have many fenestrations, small pores (holes) ranging from 70 to 100 nm in diameter
In addition to the important role of supplying the vessel wall with nerves and vasa vasorum, the tunica externa does what?
helps anchor the vessels to surrounding tissues.
Continuous capillaries are found where?
in the central nervous system, lungs, skin, skeletal and smooth muscle, and connective tissues.
Vasoconstriction of arterioles _____________________ blood pressure, and vasodilation of arterioles ___________________ blood pressure.
increase; decrease
The outermost part of the tunica interna, which forms the boundary between the tunica interna and tunica media, is the ________________ _______________ ___________
internal elastic lamina
Where can sinusoids be found within the body?
inusoids in the liver contain phagocytic cells that remove bacteria and other debris from the blood. The spleen, anterior pituitary, parathyroid, and adrenal glands also contain sinusoids.
Compared to elastic arteries, the vessel wall of muscular arteries comprises a ________________ percentage (25 percent) of the total vessel diameter.
larger
The terminal end of the arteriole, the region called the _________________ tapers toward the capillary junction.
metarteriole
The flow of blood from a metarteriole through capillaries and into a postcapillary venule (a venule that receives blood from a capillary) is called the ____________________ (micro=small) of the body.
microcirculation
When blood vessel diameter is smaller, the friction is greater, so there is more or less resistance?
more;Contraction of arteriolar smooth muscle causes vasoconstriction, which further increases resistance and decreases blood flow into capillaries supplied by that arteriole.
Medium-sized arteries are called ____________ arteries because their tunica media contains more smooth muscle and fewer elastic fibers than elastic arteries.
muscular
The ______________ venules (50 μm to 200 μm) have thicker walls across which exchanges with the interstitial fluid can no longer occur.
muscular
The tunica externa contains numerous ____________ and, especially in larger vessels, tiny blood vessels that supply the tissue of the vessel wall.
nerves
What is an example of sinusoids?
newly formed blood cells enter the bloodstream through the sinusoids of red bone marrow.
In some parts of the body, however, blood passes from one capillary network into another through a vessel called a portal vessel. Such a circulation of blood is called a _______________ ___________________.
portal system
At the metarteriole-capillary junction, the most distal muscle cell forms the ___________________ __________________ which monitors the blood flow in to the capillary; the other muscle cells in the arteriole regulate resistance (opposition to blood flow)
precapillary sphincter
As blood is ejected from the heart into elastic arteries, their walls stretch, easily accommodating the surge of blood. As they stretch, the elastic fibers momentarily store mechanical energy, functioning as a ______________ ______________
pressure reservoir
Since arterioles play a key role in regulating blood flow from arteries into capillaries by regulating resistance, they are known as ______________ vessels.
resistance
In most vessels, the tunica media is a relatively thick layer comprised mainly of ______________ _____________ cells and substantial amounts of elastic fibers
smooth muscle
The extent of _____________ _____________ ______________ in particular vessel types is crucial in the regulation of blood pressure.
smooth muscle contraction
What is angiogenesis?
the growth of new blood vessels.Several proteins (peptides) are known to promote and inhibit angiogenesis.
From innermost to outermost, the three structural layers of a generalized blood vessel are?
the tunica interna (intima), tunica media, and tunica externa (adventitia)
Unlike their thick-walled arterial counterparts, venules and veins have _________ walls that do not readily maintain their shape.
thin
Although veins are composed of essentially the same three layers as arteries, the relative thicknesses of the layers are different. The tunica interna of veins is _____________ than that of arteries; the tunica media of veins is much ______________ than in arteries, with relatively _____________smooth muscle and elastic fibers.
thinner;thinner; and little
The distal end of the vessel, which has no smooth muscle and resembles a capillary, is called a _________________ channel
thoroughfare;Such a channel provides a direct route for blood from an arteriole to a venule, thus bypassing capillaries.
The outer covering of a blood vessel, the ____________ ______________, consists of elastic and collagenous fibers (Figure 14.1a, b). It ranges in size from a thin connective tissue wrapping to the thickest layer of the blood vessel.
tunica externa
The ____________ ___________ forms the inner lining of a blood vessel and is in direct contact with the blood as it flows through the lumen (LOO-men), or interior opening, of the vessel
tunica interna (intima);Although the tunica interna has multiple parts, its tissue components contribute minimally to the thickness of the vessel wall
The ______________ _____________ is a layer composed of smooth muscle and connective tissue.
tunica media;This layer displays the greatest variation among the different vessel types
The small vessels that supply blood to the tissues of the vessel are called _______ ____________, or vessels to the vessels.
vasa vasorum
The ability of the muscle to contract and maintain a state of partial contraction is referred to as _______________ _________.
vascular tone;Vascular tone stiffens the vessel wall and is important in maintaining vessel pressure and efficient blood flow.
An increase in sympathetic stimulation typically stimulates the smooth muscle to contract, squeezing the vessel wall and narrowing the lumen. Such a decrease in the diameter of the lumen of a blood vessel is called ___________________
vasoconstriction
The increase in lumen diameter is called __________________
vasodilation
papillary muscle is with the ______________________.
ventricles
Groups of capillaries within a tissue reunite to form small veins called ______________
venules
What are the smallest venules?
venules that initially receive blood from capillaries are called postcapillary venules
What are sinusoids?
wider and more winding than other capillaries. Their endothelial cells may have unusually large fenestrations. In addition to having an incomplete or absent basement membrane, sinusoids have very large intercellular clefts that allow proteins and in some cases even blood cells to pass from a tissue into the bloodstream.
The elastic lamellae give the wall a ________________ tint.
yellowish
