LQB185 Chapter Notes - Chapter 21: Theca Interna, Tunica Externa, Tunica Media
25 May 2018
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Chapter 21 The Cardiovascular System: Blood Vessels and
Hemodynamics
21.1 Structure and Function of Blood Vessels
➢ Types of Blood Vessels
1. Arteries- carry blood away from the heart
2. Arterioles- small divided arteries coming off the main artery
3. Capillaries- arterioles when entering a tissue branch off into tiny
vessels that are capillaries. Capillaries allow exchange of substances
between blood and body tissue
4. Venules- groups of capillaries within a tissue that reunite to form
small veins
5. Veins-merging of venules makes a larger blood vessel called veins.
Veins are the blood vessels that convey blood from tissue back to
heart.
➢ Basic Structure of a Blood Vessel
- Wall of blood vessel has 3 layers
1. Epithelial inner lining (Tunic Interna)
i. Endothelium- thin layer of flattened cells (help
facilitated blood flow)
ii. Basement membrane- provides physical support,
resilience with strengthen and recoil, anchors the
endothelium to underlying connective tissue.
iii. Internal elastic lamina- thin sheet of elastic fibres,
facilitates diffusion of material to tunica media.
2. Middle layer of smooth muscle and elastic connective tissue
(Tunica Media)
3. Connective tissue outer covering (Tunica Externa)
➢ Tunic Interna
- Forms inner lining of a blood vessel
- Direct contact with the blood
➢ Tunic Media
- Muscular and connective tissue layer.
- Role is to regulate the diameter of the lumen, blood flow and
pressure
- Separating the tunica media and tunica externa are a network of
elastic fibres called external elastic lamina
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➢ Tunica Externa
- Elastic and collagen fibres, containing nerves and blood vessels
that supply blood to the tissue of the vessel called Vasa Vasorum.
➢ Arteries
- Has the same 3 layers as does a normal
blood vessel but has a thick muscular-to-
elastic tunica media.
➢ Elastic Arteries (Conducting Arteries)
- Largest arteries in the body.
- Well-defined internal and external elastic
laminae, along with a thick tunica media
that is dominated by elastic laminae
called elastic lamellae.
- Help propel blood onwards when the
ventricles are relaxing.
➢ Muscular Arteries (Distributing Arteries)
- Named because their tunica media
contains more smooth muscle and few
elastic fibres.
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Chapter 21 the cardiovascular system: blood vessels and. Types of blood vessels: arteries- carry blood away from the heart, arterioles- small divided arteries coming off the main artery, capillaries- arterioles when entering a tissue branch off into tiny vessels that are capillaries. Capillaries allow exchange of substances between blood and body tissue: venules- groups of capillaries within a tissue that reunite to form small veins, veins-merging of venules makes a larger blood vessel called veins. Veins are the blood vessels that convey blood from tissue back to heart. Wall of blood vessel has 3 layers: epithelial inner lining (tunic interna) Endothelium- thin layer of flattened cells (help facilitated blood flow) Basement membrane- provides physical support, resilience with strengthen and recoil, anchors the endothelium to underlying connective tissue. Internal elastic lamina- thin sheet of elastic fibres, facilitates diffusion of material to tunica media: middle layer of smooth muscle and elastic connective tissue (tunica media, connective tissue outer covering (tunica externa)
