21-1

Lecture 19

Circulatory System IICirculatory System II

21-2

Capillary Network

• Capillary network made of arterial and venous capillaries

• Venules drain network• Blood flows into small

veins, medium and large veins

• Valves– Allow blood to flow

toward heart but not in opposite directionFig. 23.5

21-3

Systemic Circulation: Veins

• Return blood from body to right atrium

• Major veins– Coronary sinus (heart)– Superior vena cava (head, neck, thorax, upper

limbs)– Inferior vena cava (abdomen, pelvis, lower

limbs)

• Types of veins– Superficial, deep, sinuses

21-4

How Do the Three Types of Veins Differ?

• Superficial veins– Closer to the surface of the body

• Deep veins– Typically found deeper in the body and usually next to

major arteries– Typically share names with arteries (e.g. femoral vein

next to femoral artery)

• Sinuses– A modified, slightly expanded vein that lacks smooth

muscle– Incapable of changing diameter

21-5

Veins Draining the Heart

• Cardiac veins (Great and Small)– Drain the left and right sides of the heart

• Venous blood collects in coronary sinus– Empties into right atrium

Fig. 22.9

21-6

Venous Sinuses of the Cranium

Fig. 23.11

• Dural venous sinuses receive blood that has circulated through the brain and orbit• Blood from these sinuses empties into internal jugular vein• Internal jugular vein exits skull through the jugular foramen between temporal and occipital bones

Internal jugular vein

Dural venoussinuses

21-7

Veins of Head and Neck

• Vertebral veins– Travel with vertebral artery through transverse foramina of

cervicals

– Drain cervicals, spinal cord, deep neck muscles

Vertebral veinExternal jugular vein

Internal jugular vein

Subclavian vein

Right brachiocephalicvein

Fig. 23.10

21-8

Review QuestionFusion of the brachiocephalic veins will form the(a) Subclavian vein(b) Inferior vena cava(c) External jugular vein(d)Superior vena cava(e) Axillary vein

21-9

Veins of Shoulder and Upper Limb

Fig. 23.19

• Deep veins– Radial and ulnar

veins (paired)– Brachial vein that

connects with axillary vein

• Superficial veins– Basilic vein

(becomes axillary vein)

– Cephalic vein

• Axillary vein becomes subclavian vein beneath clavicle

Superficial veinsDeep veins

Ulnar veinsRadial veins

Brachial veins

Basilic vein

Cephalic vein

Axillary vein

Subclavian vein

21-10

Veins of Abdomen and Pelvis

Fig. 23.13

Right renal vein

Left femoral vein

Left internal iliac vein

Left external iliac vein

Left common iliac vein

Inferior vena cava

Left renal vein

Diaphragm

21-11

Hepatic Portal System

• Portal system– Begins and ends in capillaries– Heart not part of system

• Hepatic portal system– Begins with viscera of abdomen– Ends with liver

Fig. 23.16

Superior mesentericvein

Ascending colon

Duodenum

Pancreas (cut)

Hepatic portalvein

Liver

Inferior venacava

Diaphragm

Stomach

Gastric veins

Spleen

Splenic vein

Inferior mesentericvein

Small intestine

Descendingcolon

21-12

Veins of Pelvis and Lower Limb• Deep veins

– Anterior and posterior tibial veins

– Popliteal vein– Femoral vein

• Superficial veins– Great saphenous

vein

• External iliac vein

• Internal iliac veinSuperficial veinsDeep veins

Posterior viewAnterior view

Great saphenousvein

Femoral vein

Popliteal vein

Anterior tibialveinsPosterior tibialveins

Great saphenousvein

Internal iliac vein

External iliac vein

Common iliac vein

Fig. 23.20

21-13

Valves in Veins

-Found in medium size veins

-Allow a one-way direction of blood back to the heart

Varicose Veins-Found in superficial veins because there isn’t skeletal muscles around the vein. -Hemorroids

21-14

Points to RememberPoints to Remember1. Three major types of veins: superficial,

deep and sinuses

2. Venous blood carried to heart by coronary sinus, superior vena cava and inferior vena cava

3. Hepatic portal system - not connected directly to heart

21-15

Questions?