Lecture 19 Circulatory System II 1 Capillary Network

Lecture 19 Circulatory System II 1

Capillary Network • Capillary network made of arterial and venous capillaries • Venules drain network • Blood flows into small veins, medium and large veins • Valves Fig. 23. 5 – Allow blood to flow toward heart but not in opposite direction 2

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 3

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 4

Veins Draining the Heart Fig. 22. 9 • Cardiac veins (Great and Small) – Drain the left and right sides of the heart • Venous blood collects in coronary sinus – Empties into right atrium 5

Venous Sinuses of the Cranium • 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 Dural venous sinuses Internal jugular vein Fig. 23. 11 6

Veins of Head and Neck Vertebral vein External jugular vein Internal jugular vein Subclavian vein Right brachiocephalic vein Fig. 23. 10 • Vertebral veins – Travel with vertebral artery through transverse foramina of cervicals – Drain cervicals, spinal cord, deep neck muscles 7

Review Question Fusion 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 8

Veins of Shoulder and Upper Limb Subclavian vein • Deep veins – Radial and ulnar veins (paired) – Brachial vein that connects with axillary vein Axillary vein Cephalic vein Basilic vein Brachial veins • Superficial veins – Basilic vein (becomes axillary vein) – Cephalic vein • Axillary vein becomes subclavian vein beneath clavicle Radial veins Fig. 23. 19 Ulnar veins Superficial veins Deep veins 9

Veins of Abdomen and Pelvis Diaphragm Right renal vein Left renal vein Inferior vena cava Left common iliac vein Left external iliac vein Left internal iliac vein Left femoral vein Fig. 23. 13 10

Hepatic Portal System Inferior vena cava Diaphragm Liver Hepatic portal vein Duodenum Stomach Gastric veins Spleen Splenic vein Pancreas (cut) Superior mesenteric vein Ascending colon • Portal system – Begins and ends in capillaries – Heart not part of system Inferior mesenteric vein Descending colon Small intestine Fig. 23. 16 • Hepatic portal system – Begins with viscera of abdomen – Ends with liver 11

Veins of Pelvis and Lower Limb • Deep veins – Anterior and posterior tibial veins – Popliteal vein – Femoral vein Anterior view Posterior view Common iliac vein External iliac vein Internal iliac vein Femoral vein Great saphenous vein • Superficial veins Popliteal vein – Great saphenous vein Anterior tibial veins Posterior tibial veins • External iliac vein • Internal iliac vein Great saphenous vein Deep veins Superficial veins Fig. 23. 20 12

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 13

Points to Remember 1. 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 14

Questions? 15