20 Blood Vessels

I. Types of Blood Vessels Heart to ► A. Arteries - carry blood away from the heart ► B. Arterioles - the smallest arteries ► C. Capillaries - the smallest blood vessels (exchange occurs here) ► D. Venules - receive blood from capillaries ► E. Veins - receive blood from venules ► ► to Heart

II. Structure of Blood Vessels (3 layers) A. Lumen – space that blood flows through B. Tunica intima - innermost tunic 1. lines all blood vessels (arteries, veins, etc.) 2. simple squamous epithelium = endothelium C. Tunica media - sheets of smooth muscle and elastin 1. sympathetics control vasoconstriction and vasodilation = B.P. D. Tunica externa 1. Collagen fibers protect and reinforce 2. Contains nerve fibers and lymphatic vessels 3. Vasa vasorum of larger vessels nourishes external layer

Tunica intima Artery Endothelium Vein Tunica media Tunica externa Vasa vasorum Valve Capillary network Lumen Lumen Basement membrane Capillary Endothelial cells

• Internal elastic membrane • External elastic membrane Tunica intima • Endothelium • Subendothelial layer • Internal elastic membrane Tunica media (smooth muscle and elastic fibers) Valve • External elastic membrane Tunica externa (collagen fibers) • Vasa vasorum Lumen Lumen Artery Capillary network Vein Basement membrane Endothelial cells © 2013 Pearson Education, Inc. Capillary

Artery Vein

III. Types of Arteries A. Elastic Arteries 1. thick-walled arteries with elastin in all three layers 2. large lumen offers least resistance = easier blood flow 3. act as pressure reservoirs = expand and recoil as blood leaves heart 4. aorta and its major branches B. Muscular Arteries 1. distal to elastic arteries = delivers blood to the body organs 2. thick tunica media with more smooth muscle 3. active in vasoconstriction C. Arterioles 1. smallest arteries that lead to the capillary beds 2. control direction of blood flow via vasoconstriction

IV. Capillaries A. General Structure 1. microscopic blood vessel = one blood cell in diameter! 2. very thin tunica intima = easy permeability to fluid and molecules 3. pericytes help stabilize the walls and help control permeability B. Major Function 1. exchange of gases, nutrients, waste compounds, hormones, etc.

Red blood cells passing through a capillary (512).

C. Continuous Capillaries 1. most common type of capillary 2. occur in most organs (especially skin and muscle) 3. tight junctions and desmosomes join epithelial cells 4. Intercellular clefts = limited passage of fluids and small solutes a. blood-brain barrier – only certain molecules can pass

Pericyte Red blood cell in lumen Intercellular cleft Endothelial cell Endothelial nucleus Basement membrane Pinocytotic vesicles Tight junction Continuous capillary. Least permeable, and most common (e.g., skin, muscle).

D. Fenestrated Capillaries 1. some endothelial cells contain pores (fenestrations) 2. more permeable than continuous capillaries 3. function in absoprtion or filtration 4. located in small intestine, endocrine glands and kidney

Pinocytotic vesicles Red blood cell in lumen Fenestrations (pores) Endothelial nucleus Intercellular cleft Basement membrane Endothelial cell Tight junction Fenestrated capillary. Large fenestrations (pores) increase permeability. Occurs in areas of active absorption or filtration (e.g., kidney, small intestine).

E. Sinusoid Capillaries 1. fewer tight junctions 2. usually fenestrated 3. larger intercellular clefts and large lumens 4. large molecules pass between blood and surrounding tissues 5. found only in the liver, bone marrow, spleen, adrenal medulla 6. in the liver, hepatic macrophages in lining to destroy bacteria

Endothelial cell Red blood cell in lumen Large intercellular cleft Tight junction Nucleus of endothelial cell Incomplete basement membrane Sinusoid capillary. Most permeable. Occurs in special locations (e.g., liver, bone marrow, spleen).

F. Capillary Transport 1. direct diffusion 2. through intercellular clefts 3. through cytoplasmic vesicles 4. through fenestrations G. Blood brain barrier 1. capillaries have complete tight junctions 2. no intercellular clefts are present 3. vital molecules pass through a. highly selective transport mechanisms 4. NOT a barrier against: a. Oxygen, carbon dioxide, and some anesthetics

H. Blood Flow through Capillary Bed 1. vascular shunt (meta-arteriole) a. connects terminal arteriole and postcapillary venule 2. true capillaries a. 10-100 per capillary bed b. branch off metarteriole or terminal arteriole 3. Precapillary sphincters regulate blood flow into true capillaries a. blood may go through true capillaries or through shunt b. regulated by local chemical conditions and vasomotor nerves c. example: eating and relaxing i. blood flow in the digestive system ii. abdominal cramps and indigestion = eating then running!

Vascular shunt Precapillary sphincters Metarteriole Thoroughfare channel True capillaries Terminal arteriole Postcapillary venule Sphincters open—blood flows through true capillaries.

Terminal arteriole Postcapillary venule Sphincters closed—blood flows through metarteriole – thoroughfare channel and bypasses true capillaries.

V. Veins A. Venules join to form veins B. Have thinner walls, larger lumens compared with corresponding arteries C. Thin tunica media; thick tunica externa of collagen fibers and elastic networks D. Called capacitance vessels (blood reservoirs); up to 65% of blood supply E. Blood pressure lower than in arteries (walls don’t burst!) F. Adaptations ensure return of blood to heart despite low pressure 1. Large-diameter lumens offer little resistance 2. Venous valves prevent backflow of blood a. most abundant in veins of limbs 3. Venous sinuses: flattened veins with extremely thin walls (e.g., coronary sinus of the heart & dural sinuses of the brain)

a. particularly in limbs b. prevent backflow of blood G. Mechanisms to counteract low venous pressure 1. Valves in some veins a. particularly in limbs b. prevent backflow of blood c. not located in veins of thoracic and abdominal cavities 2. Skeletal muscle pump a. muscles press against thin-walled veins

Contracted skeletal muscle The Muscular Pump in Veins Venous valve (open) Contracted skeletal muscle Venous valve (closed) Varicose Vein Vein Direction of blood flow

VI. Vascular Anastomoses A. Vessels interconnect to form vascular anastomoses 1. organs receive blood from more than one arterial source 2. neighboring arteries form arterial anastomoses 3. provide collateral channels 4. veins anastomose more frequently than arteries

Blood Vessels to Know (Study Guide)

KNOW THIS!! Arteries of the head and trunk Internal carotid artery External carotid artery Common carotid arteries KNOW THIS!! Vertebral artery Arteries that supply the upper limb Subclavian artery Subclavian artery Brachiocephalic trunk Aortic arch Axillary artery Ascending aorta Coronary artery Thoracic aorta (above diaphragm) Celiac trunk Brachial artery Abdominal aorta Superior mesenteric artery Renal artery Radial artery Gonadal artery Ulnar artery Inferior mesenteric artery Common iliac artery Internal iliac artery Deep palmar arch Superficial palmar arch Digital arteries Arteries that supply the lower limb External iliac artery Femoral artery Popliteal artery Anterior tibial artery Posterior tibial artery Arcuate artery Anterior view

KNOW THIS!! Anterior view

KNOW THIS!! 30 Veins of the head and trunk Dural venous sinuses External jugular vein Vertebral vein Veins that drain the upper limb Internal jugular vein Subclavian vein Right and left brachiocephalic veins Axillary vein Cephalic vein Superior vena cava Brachial vein Great cardiac vein Basilic vein Hepatic veins Splenic vein Median cubital vein Hepatic portal vein Ulnar vein Renal vein Radial vein Superior mesenteric vein Inferior mesenteric vein Digital veins Inferior vena cava Common iliac vein Veins that drain the lower limb Internal iliac vein External iliac vein Femoral vein Great saphenous vein Popliteal vein KNOW THIS!! Posterior tibial vein Anterior tibial vein Small saphenous vein Dorsal venous arch Dorsal metatarsal veins 30

KNOW THIS!! 31

VII. Two Main Circulations A. Pulmonary circulation: short loop that runs from heart to lungs and back to heart B. Systemic circulation: long loop to all parts of body and back to heart

Pulmonary Circuit Pulmonary capillaries of the R. lung Pulmonary L. lung R. pulmonary artery L. pulmonary artery Pulmonary Circuit To systemic circulation Pulmonary trunk R. pulmonary veins From systemic circulation RA LA L. pulmonary veins RV LV Schematic flowchart.

Pulmonary Circuit RV LV Left pulmonary artery Air-filled alveolus of lung Aortic arch Pulmonary trunk Right pulmonary artery Three lobar arteries to right lung Pulmonary capillary Gas exchange Two lobar arteries to left lung Pulmonary veins Pulmonary veins Right atrium Left atrium Right ventricle Left ventricle Illustration. The pulmonary arterial system is shown in blue to indicate that the blood it carries is oxygen-poor. The pulmonary venous drainage is shown in red to indicate that the blood it transports is oxygen-rich.

Systemic Circuit Common carotid arteries to head and subclavian upper limbs Capillary beds of head and upper limbs Superior vena cava Aortic arch Systemic Circuit Aorta RA LA RV LV Azygos system Thoracic aorta Venous drainage Arterial blood Inferior vena cava Capillary beds of mediastinal structures and thorax walls Diaphragm Abdominal aorta Capillary beds of digestive viscera, spleen, pancreas, kidneys Inferior vena cava Capillary beds of gonads, pelvis, and lower limbs

VI. The Aorta and Its Branches A. Ascending aorta - arises from the left ventricle 1. coronary arteries 2. Aortic arch - lies posterior to the manubrium ► brachiocephalic trunk 1. right commom carotid 2. right subclavian ► left common carotid ► left subclavian arteries B. Descending aorta ► Thoracic aorta ► Abdominal aorta Will Review in the Lab !!

Left common carotid artery Right common carotid artery Left subclavian artery Right subclavian artery Left subclavian vein Left brachiocephalic vein Brachiocephalic trunk Aortic arch Thoracic aorta Ascending aorta

Aorta Ascending artery Aortic Arch Descending aorta 3D view part I Major arteries of the systemic circulation. Aorta Ascending artery Aortic Arch Descending aorta Left coronary artery Right coronary artery Thoracic aorta Abdominal aorta Left & right common iliac arteries brachiocephalic Left common carotid artery Left subclavian artery Right common carotid artery Right subclavian artery 3D view part II 3D view part I http://www.youtube.com/ watch?v=20346sgZ3dA http://www.youtube.com/ watch?v=LQne1SILsVk

Cerebral arterial circle Brachiocephalic trunk R. and L. anterior cerebral arteries R. Middle cerebral artery Anterior communicat- ing artery Cerebral arterial circle R. and L. Posterior communicat- ing arteries Ophthalmic artery R. posterior cerebral artery Basilar artery Superficial temporal artery Maxillary artery R. and L. vertebral arteries Circle of Willis: provides an alternate set for blood to reach the brain in case of impaired blood flow! Occipital artery R. and L. internal carotid arteries Facial artery Lingual artery R. and L. external carotid arteries Superior thyroid artery R. and L. common carotid arteries http://www.youtube.com/watch?v=9hhfM7rQHiM R. and L. subclavian arteries Brachiocephalic trunk Aortic arch Schematic flowchart

Ophthalmic artery Branches of the external carotid artery Vertebral artery • Superficial temporal artery Internal carotid artery • Maxillary artery • Occipital artery External carotid artery • Facial artery • Lingual artery • Superior thyroid artery Common carotid artery Subclavian artery Brachiocephalic trunk

http://www.youtube.com/watch?v=_YBxDhoS9fU Anterior Cerebral arterial circle (circle of Willis) Optic chiasma • Anterior communicating artery Middle cerebral artery • Anterior cerebral artery Internal carotid artery • Posterior communicating artery Mammillary body • Posterior cerebral artery Basilar artery Vertebral artery Pons Occipital lobe Cerebellum Posterior http://www.youtube.com/watch?v=_YBxDhoS9fU

Superficial palmar arch Illustration, anterior view Vertebral artery Common carotid arteries Right subclavian artery Left subclavian artery Brachiocephalic trunk Axillary artery Brachial artery Thoracic aorta Radial artery Ulnar artery Deep palmar arch Superficial palmar arch Digital arteries Illustration, anterior view

L. gastroepiploic artery Diaphragm Abdominal aorta L. gastric artery R. gastric artery Common hepatic artery Hepatic artery proper L Celiac trunk Gastro- duodenal artery Splenic artery R R. gastroepiploic artery L. gastroepiploic artery Intestinal arteries http://www.youtube.com/ watch?v=hoVRH670BOc Middle colic artery Superior mesenteric artery R. colic artery Renal arteries Gonadal arteries Ileocolic artery Sigmoidal arteries Inferior mesenteric artery L. colic artery Superior rectal artery Lumbar arteries Median sacral artery Common iliac arteries Schematic flowchart.

Common iliac artery Obturator artery Femoral artery Popliteal artery Anterior tibial artery Posterior tibial artery Fibular artery Dorsalis pedis artery Arcuate artery Dorsal metatarsal arteries Anterior view

Ophthalmic vein Facial vein Occipital vein External jugular vein Vertebral vein Internal jugular vein Brachiocephalic vein Subclavian vein Superior vena cava Veins of the head and neck, right superficial aspect

Brachiocephalic veins Right subclavian vein Axillary vein Superior vena cava Brachial vein Inferior vena cava Ulnar vein Radial vein Deep venous palmar arch Superficial venous palmar arch Digital veins Anterior view

Hepatic veins Inferior vena cava Right suprarenal vein Renal veins Right gonadal vein Lumbar veins Common iliac vein External iliac vein Internal iliac vein Tributaries of the inferior vena cava. Venous drainage of abdominal organs not drained by the hepatic portal vein.

The hepatic portal circulation. Hepatic veins Liver Inferior vena cava Hepatic portal vein Blood drained from the digestive system; rich is nutrients; liver is responsible for maintaining the conc of glucose, proteins, etc + phagocytes cleanse the blood Inferior mesenteric vein Superior mesenteric vein Small intestine

Common iliac vein Femoral vein Great saphenous vein (superficial) The longest vein! Popliteal vein Fibular vein Anterior tibial vein Dorsalis pedis vein Dorsal venous arch Dorsal metatarsal veins Anterior view