Blood Vessels

Circulatory System Three basic components: Heart - serves as pump that establishes the pressure gradient needed for blood to flow to tissues Blood - transport medium within which materials being transported are dissolved or suspended Blood vessels - passageways through which blood is distributed from heart to all parts of body and back to heart

arteries → arterioles → capillaries → venules → veins Types Of Blood Vessels Arteries – carry blood away from the heart Capillaries – smallest blood vessels The site of exchange of molecules between blood and tissue fluid Veins – carry blood toward the heart arteries → arterioles → capillaries → venules → veins

Functions Of Blood Vessels Arteries - carry blood away from heart Arterioles - small arteries that deliver blood to capillaries Capillaries – thin walled vessels allow for exchange between blood and tissue cells Venules - collect and drain blood into veins Veins - return blood to heart

Structure Of Blood Vessels Composed of three layers (tunics) Tunica intima – composed of simple squamous epithelium Tunica media – sheets of smooth muscle Contraction – vasoconstriction Relaxation – vasodilation Tunica externa – composed of connective tissue Lumen - central blood-filled space of a vessel

Structural Differences Arteries have thicker tunica media and narrower lumens Veins have thicker tunica externa Arteries have more elastic and collagen fibers Veins have larger lumens and valves

Types Of Arteries Elastic arteries – the largest arteries Diameters range from 2.5 cm to 1 cm Includes the aorta and its major branches Sometimes called conducting arteries High elastin content dampens surge of blood pressure

Types Of Arteries Muscular (distributing) arteries Lie distal to elastic arteries Diameters range from 1 cm to 0.3 mm Includes most named arteries Tunica media is thick Unique features Internal and external elastic laminae

Types Of Arteries Arterioles Smallest arteries Diameters range from 0.3 mm to 10 µm Larger arterioles possess all three tunics Diameter of arterioles controlled by: Local factors in the tissues Sympathetic nervous system

Capillaries Smallest blood vessels Diameter from 8–10 µm Red blood cells pass through single file Endothelial cells – held together by tight junctions and desmosomes Routes into and out of capillaries Direct diffusion Through intercellular clefts - gaps of unjoined membrane where small molecules can enter and exit Through fenestrations - pores

Capillaries Site-specific functions of capillaries Lungs – oxygen enters blood, carbon dioxide leaves Small intestines – receive digested nutrients Endocrine glands – pick up hormones Kidneys – removal of nitrogenous wastes Tendons and ligaments – poorly vascularized Epithelia and cartilage – avascular, receive nutrients from nearby CT

Capillaries Three types of capillary Continuous – most common Fenestrated – have pores Sinusoids

Sinusoids Wide, leaky capillaries found in some organs Usually fenestrated Have large diameters Intercellular clefts are wide open Occur in bone marrow, liver, spleen and lymphoid tissue

Capillary Beds An interconnected network of vessels running through tissues Consists of: Collateral arteries feeding an arteriole Metarterioles Arteriovenous anastomoses Capillaries Venules

Capillary Beds Precapillary sphincters - regulate the flow of blood to tissues

Veins Conduct blood from capillaries toward the heart Blood pressure is much lower than in arteries Smallest veins – called venules Diameters from 8 – 100 µm Smallest venules – called postcapillary venules Venules join to form veins

Role Of Veins To return blood to the heart, veins have special adaptations Large-diameter lumens, which offer little resistance to flow Valves (resembling semilunar heart valves), which prevent backflow of blood Skeletal muscle pump - muscles press against thin-walled veins

Pulmonary Circulation Consists of blood vessels that take the blood to and from the lungs for the purpose of gas exchange Pulmonary Trunk: oxygen-poor blood leaves the right ventricle via the pulmonary trunk; large artery that branches to left and right pulmonary arteries Pulmonary Arteries : take the blood to the lung where oxygen is picked up and CO2 is left off Pulmonary Veins: blood returns to the heart via four pulmonary veins that go to the left atrium

Systemic Circulation Consists of blood vessels that extend to and from the heart delivers oxygen and nutrients to body tissues picks up CO2 and waste products

The Aorta And Vena Cava Ascending aorta – arises from the left ventricle branches to form coronary arteries Aortic arch – lies posterior to the manubrium branches to form Brachiocephalic trunk Left common carotid Left subclavian arteries Descending aorta – continues from the aortic arch Thoracic aorta – in the region of T5–T12 Abdominal aorta – ends at L4 Divides into right and left common iliac arteries Superior/Inferior vena cava returns blood from the systemic veins to the heart

The Hepatic Portal System A specialized part of the vascular circuit Picks up digested nutrients Delivers nutrients to the liver for processing

Veins Of The Hepatic Portal System Hepatic veins Gastric veins Liver Spleen Inferior vena cava Hepatic portal vein Splenic vein Inferior mesenteric vein Superior mesenteric vein Small intestine Large intestine Rectum

Cerebral Arterial Circle (Circle Of Willis) “Circle” equalizes blood pressure in the brain and can provide alternative channels if one vessel becomes blocked The circle is formed from : posterior cerebral arteries, posterior communicating arteries, internal carotid arteries, anterior cerebral arteries, and anterior communicating arteries Anterior Cerebral arterial circle (circle of Willis) • Anterior communicating artery Middle cerebral artery • Anterior cerebral artery Internal carotid artery • Posterior communicating artery • Posterior cerebral artery Basilar artery Vertebral artery Posterior (c)

Arteries Of The Right Upper Limb And Thorax Vertebral artery Common carotid arteries Left axillary artery Right subclavian Left subclavian Anterior intercostal Descending aorta Brachiocephalic trunk Axillary artery Radial Ulnar Brachial artery Suprascapular artery

Arteries Of The Head And Neck, Right Aspect Brachiocephalic trunk Internal thoracic artery Internal carotid artery Subclavian (a) Axillary External Common

Major Branches Of The Abdominal Aorta Diaphragm Adrenal gland Suprarenal artery Celiac trunk Renal artery Superior mesenteric artery Kidney Gonadal artery Abdominal aorta Inferior mesenteric artery Common iliac artery

The Celiac Trunk And Its Main Branches Liver Inferior vena cava Celiac trunk Left gastric artery Common hepatic artery Splenic artery Right gastric artery Spleen Superior mesenteric artery Abdominal aorta (b)

Arteries Of The Right Pelvis And Lower Limb Common iliac artery Femoral artery Popliteal artery Anterior tibial artery Posterior tibial artery Fibular artery Internal iliac artery External iliac artery Anterior tibial artery Posterior tibial Anterior view Posterior view

Flow Chart Summarizing Main Systemic Arteries Figure 19.17

Systemic Veins Three major veins enter the right atrium Superficial veins lie just beneath the skin Multivein bundles – venous plexuses Unusual patterns of venous drainage Dural sinuses Hepatic portal system

Venae Cavae and Tributaries Superior vena cava Returns blood from body regions superior to the diaphragm Inferior vena cava Returns blood from body regions inferior to the diaphragm Superior and inferior vena cava Join the right atrium

Major veins of the systemic circulation. Renal vein Splenic vein Basilic vein Brachial vein Cephalic vein Dural sinuses External jugular vein Vertebral vein Internal jugular vein Superior vena cava Axillary vein Great cardiac vein Hepatic veins Hepatic portal vein Superior mesenteric vein Inferior vena cava Ulnar vein Radial vein Common iliac vein External iliac vein Internal iliac vein Digital veins Femoral vein Great saphenous vein Popliteal vein Posterior tibial vein Anterior tibial vein Fibular vein Inferior mesenteric vein Median cubital vein Right and left brachiocephalic veins Subclavian vein

Dural Sinuses In The Cranium Superior sagittal sinus Falx cerebri Inferior sagittal sinus Straight sinus Cavernous sinus Junction of sinuses Transverse sinuses Sigmoid sinus Jugular foramen Right internal jugular vein (b)

Veins of the head and Neck Ophthalmic vein Superficial temporal vein Facial vein Occipital vein Posterior auricular vein External jugular vein Vertebral vein Internal jugular vein Superior and middle thyroid veins Brachiocephalic vein Subclavian vein Superior vena cava (a)

Veins Of The Right Upper Limb And Thorax Wall Internal jugular vein External jugular vein Brachiocephalic veins Right subclavian vein Left subclavian vein Superior vena cava Axillary vein Azygos vein Accessory hemiazygos vein Brachial vein Cephalic vein Basilic vein Hemiazygos vein Posterior intercostals Inferior vena cava Median cubital vein Ascending lumbar vein Median vein of the forearm Basilic vein Cephalic vein Ulnar vein Radial vein Deep palmar venous arch Superficial palmar venous arch Digital veins (a)

Antecubital Fossa Form anastomese frequently Median cubital vein is used to obtain blood or administer IV fluids Figure 19.22

Veins Of The Right Upper Limb And Thorax Wall Brachiocephalic veins Superior vena cava 1 Left superior intercostal vein 2 3 4 Azygos vein 5 Accessory hemiazygos vein 6 7 Intercostal veins Hemiazygos vein 8 9 Intercostal veins 10 11 Ascending lumbar vein 12 Inferior vena cava Renal vein (b)

Veins of the Abdomen Lumbar veins Gonadal (testicular or ovarian) veins Renal veins Suprarenal veins Hepatic veins

Tributaries Of The Inferior Vena Cava Inferior phrenic vein Hepatic veins Inferior vena cava Left suprarenal vein Right suprarenal vein Renal veins Left ascending lumbar vein Right gonadal vein Lumbar veins Left gonadal vein Common iliac vein External iliac vein Internal iliac vein

Dissection of the posterior abdominal wall Diaphragm Right Left Inferior vena cava Hepatic veins Renal veins Common iliac veins Abdominal aorta

Veins of the Pelvis and Lower Limbs Deep veins Share the name of the accompanying artery Superficial veins Great saphenous vein empties into the femoral vein Small saphenous vein empties into the popliteal vein

Veins Of The Right Lower Limb And Pelvis Popliteal vein Common iliac vein Fibular (peroneal) vein Anterior tibial vein Dorsalis pedis vein Dorsal venous arch Metatarsal veins Internal iliac vein External iliac vein Inguinal ligament Femoral vein Great saphenous vein (superficial) Great saphenous vein Small saphenous vein (superficial) Posterior tibial vein Plantar veins Plantar arch Digital veins (a)

Flowchart Summarizing The Main Veins Veins of R. upper limb R. External jugular – superficial head and neck R. vertebral – cervical spinal cord and vertebrae Intracranial dural sinuses R. internal jugular – dural sinuses of the brain R. subclavian – R. head, neck, and upper limb R. axillary Same as R. brachiocephalic R. brachiocephalic – R. side of head and R. upper limb L. brachiocephalic – L. side of head and L. upper limb Superior vena cava – runs from union of brachiocephalic veins behind manubrium to R. atrium Azygos system – drains much of thorax R. atrium of heart Diaphragm Inferior vena cava – runs from junction of common iliac veins at L5 to R. atrium of heart L. and R. hepatic veins – liver R. suprarenal (L. suprarenal drains into L. renal vein) – adrenal glands L. and R. renal veins – kidneys R. gonadal (L. gonadal drains into L. renal vein) – testis or ovary Lumbar veins (several pairs) – posterior abdominal wall R. common iliac – pelvis and R. lower limb L. common iliac – pelvis and L. lower limb Veins of R. lower limb Veins of L. lower limb (a)