Blood Vessels - Tunics

Question 1

Elastic Arteries

Answer 1

Aorta and It’s Main Branches

T. Intima: Endothelial Cells, Subendothelial Conn Tissue, inconspicuous IEL, fenestrated

T. Media: Thickest layer, 40-70 layers of elastic lamellae, smooth muscle cells, Type III collagen

T. Adventitia: Dense Irregular Connective Tissue plus small blood vessels and nerves.

Question 2

Muscular Arteries

Answer 2

Medium sized vessels that are named, most abundant in body. aka Distributing Arteries

T. Intima: Endothelial Cells, distinct undulating IEL (scallop shaped).

T. Media: Thickest layer, 8 to 40 layers of mostly smooth muscle cells in circular arrangement. Few elastic fibers & collagen. Distinct EEL.

T. Adventitia: Dense Irregular Connective Tissue with collagen & elastic fibers plus small blood vessels and nerves.

Question 3

Small Arteries

Answer 3

T. Intima: endothelial cells, minimal sub endothelial connective tissue.

T. Media: 3-8 layers of smooth muscle cells in a circular arrangement.

T. Adventitia: type 1 collagen. Ill-defined, blends in with surrounding connective tissue.

Question 4

Arterioles

Answer 4

Smallest arteries. Can be closed down. Major blood pressure determinants.

T. Intima: Endothelium

T. Media: 1-2 layers of smooth muscle cells

T. Adventitia: ill-defined. Blends in with surrounding conn tissue.

Question 5

Capillaries (general)

Answer 5

Single layer of endothelial cells plus basal lamina. Permits material exchange. May be encircled by pericytes (Rouget cells)

Question 6

Continuous / Somatic Capillary

Answer 6

Continuous basal lamina. Uninterrupted endothelium. Tight junctions present between cells.

Complete control over diffusion, endocytosis, exocytosis.

Vessels that form barriers in organs (brain, thymus, lung, testes, etc.)

Question 7

Fenestrated / Visceral Capillary

Answer 7

Continuous basal lamina. Fenestrations present within endothelial cell membrane with numerous pinocytotic vesicles. Tight junctions present between cells.

Allows certain secretions.

Vessels in peptide secreting endocrine organs, ciliary processes (eye), choroid plexus (ventricles), kidney (glomeruli), lamina propria of GI tract.

Question 8

Discontinuous / Sinusoidal Capillary

Answer 8

Discontinuous basal lamina. Large fenestrations present, wide irregular intercellular gaps. Absence of tight junctions.

Allows passage of macromolecules.

Liver, Spleen, Bone Marrow.