Md1 Histology Block3 Circulatory 3

Front 1

Veins
___? of the total blood volume

Back 1

70%

Front 2

Veins:
walls which are thinner
more supple
less elastic

Back 2

still distensible (compliance
Capacitance or Reservoir vessels)

Front 3

Vein layers

Back 3

tunica intima
tunica media
tunica adventitia

Front 4

Classification of Veins

Back 4

Venules (postcapillary & muscular types)
Small to medium sized-veins
Large veins

Front 5

Tunica intima: is thin. ***

3ct

Back 5

1 Endothelial cells

2 subendothelial

3It does not form a distinct internal elastic lamina.

Front 6

Special Types of Veins

iliac, femoral, saphenous, cephalic, basilar and umblical veins, there are longitudinal smooth muscle fibers in the subendothelial connective tissue layer of the tunica intima.

Back 6

.

Front 7

Special Types of Veins

In certain veins the longitudinal orientation of cellular elements is also noticed in the innermost layer of tunica media.

Back 7

.

Front 8

Special Types of Veins

In a considerable portion of the inferior vena cava, the tunica media is absent, and the well-developed longitudinal muscle bundles of the tunica adventitia are directly adjacent to the intima.

Back 8

.

Front 9

Large veins

The adventitial muscle serves to strengthen the wall and prevent distension of the vessel. The circular and longitudinal muscle arrangement of smooth muscle in the vessels of lower extremities may oppose the action of gravity by providing a peristaltic pumping of the blood up to the heart.

Many vasa vasorums are present in adventitia.

Back 9

.

Front 10

Tunica adventitia: layer description:
3ct

Back 10

-a zone of dense fibroelastic connective tissue

-middle zone contains many longitudinal muscle fibers

-outermost zone consists only of a coarse network of collagenous and elastic fibers.

Hint 10

Front 11

Special Types of Veins

pulmonary veins, the media is well

Back 11

developed

Front 12

Special Types of Veins

Smooth muscle is particularly prominent in all the layers of the veins in

Back 12

pregnant uterus

Front 13

Special Types of Veins

Other veins are entirely devoid of

Back 13

-smooth muscle

-tissue and consequently lack a
tunica media.

Front 14

Special Types of Veins

Other veins are entirely devoid of smooth muscle tissue and consequently lack a tunica media. In this group belong the

Back 14

-veins of the maternal part of the -placenta
-spinal pia mater
-retina
-sinuses of the dura mater
-cerebral veins
-nailbed
-trabeculae of the spleen.

Front 15

extends for a distance into the adventitia of the venae cavae and pulmonary veins near their entrance into the heart. =

Back 15

Cardiac muscle

Front 16

the blood is shunted from the arterioles directly into the venules without having to circulate through a capillary network is called =

Back 16

Arteriovenous Anastomoses

Front 17

Arteriovenous Anastomoses
located where =

Back 17

nail beds
auricle of the ear, the arteriovenous anastomoses

Front 18

Clinical Note

A vein is said to be ______ when its diameter is greater than normal and it is elongated and tortuous.

Back 18

vericosed

Front 19

Vericose Veins
definition =

Back 19

: A vein is said to be vericosed when its diameter is greater than normal and it is elongated and tortuous.

Front 20

Vericose veins occur at three sites:

Back 20

superficial veins of lower limb
veins at the lower end of the esophagus (called esophageal varices)

***veins of the anal canal (called hemorrhoids).