Blood Vessels

Dr. Emad Abu AlrubAAUJ

Blood Vessels

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

Circulatory System

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 heartarteries → arterioles → capillaries → venules → veins

Types 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

Functions 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

Structure Of Blood Vessels

• 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

Structural Differences

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

Types Of Arteries

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

Capillaries

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

Sinusoids

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

Capillary Beds

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

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

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

Pulmonary 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

Systemic Circulation

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 Aorta And Vena Cava

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

The Hepatic Portal System

Veins Of The Hepatic Portal System

Hepatic veins

LiverSpleenGastric veins

Inferior vena cavaSplenic vein

Inferiormesenteric vein

Superiormesenteric vein

Large intestine

Hepatic portal vein

Small intestine

Rectum

“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

Cerebral Arterial Circle (Circle Of Willis)

(c)

Middle cerebralartery

Internalcarotidartery

Cerebral arterial circle (circle of Willis)

Anterior

Posterior

• Posterior cerebral arteryBasilar artery

Vertebral artery

• Posterior communicating artery

• Anterior cerebral artery

• Anterior communicating artery

  Arteries Of The Right Upper Limb And Thorax

(b)

Vertebral arteryCommon carotidarteries

Left axillaryartery

Right subclavianarteryLeft subclavianartery

Anterior intercostalartery

Descending aorta

Brachiocephalictrunk

Axillary artery

Radial arteryUlnar artery

Brachial artery

Suprascapular artery

 Arteries Of The Head And Neck/ Right Aspect

BrachiocephalictrunkInternal thoracicartery

Internalcarotid artery

Subclavianartery

(a)

Axillaryartery

Externalcarotid artery

Commoncarotid artery

 Major Branches Of The Abdominal Aorta

Adrenalgland

Celiac trunk

Kidney

Abdominal aorta

Diaphragm

Suprarenal artery

Renal arterySuperiormesenteric artery

Gonadalartery

Inferiormesenteric artery

Common iliacartery

The Celiac Trunk And Its Main Branches

(b)

Liver

Left gastric artery

Superior mesentericartery

SpleenSplenic artery

Inferior vena cava

Celiac trunk

Common hepatic arteryRight gastric artery

Abdominal aorta

 Arteries Of The Right Pelvis And Lower Limb

(a)

(b)

Common iliac artery

Femoral artery

Popliteal artery

Anterior tibial arteryPosterior tibial artery

Fibular artery

Internal iliac artery

External iliac arteryPopliteal artery

Anterior tibial artery

Fibular arteryPosterior tibial artery

Anterior view

Posterior view

Flow Chart Summarizing Main Systemic Arteries

Figure 19.17

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

Systemic Veins

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

Venae Cavae and Tributaries

Major veins of the systemic circulation.

Renal vein

Splenic veinBasilic veinBrachial veinCephalic vein

Dural sinusesExternal jugular veinVertebral veinInternal jugular veinSuperior vena cavaAxillary veinGreat cardiac veinHepatic veinsHepatic portal veinSuperior mesenteric veinInferior vena cava

Ulnar veinRadial vein

Common iliac veinExternal iliac vein

Internal iliac veinDigital veins

Femoral veinGreat saphenous veinPopliteal veinPosterior tibial veinAnterior tibial veinFibular vein

Inferior mesenteric vein

Median cubital vein

Right and leftbrachiocephalic veins

Subclavian vein

Dural Sinuses In The CraniumSuperior sagittalsinusFalx cerebri

Inferior sagittalsinusStraight sinusCavernous sinusJunction of sinusesTransverse sinuses

Jugular foramen

(b)

Right internaljugular vein

Sigmoid sinus

Veins of the head and Neck

Ophthalmic vein

Superficialtemporal vein

Facial vein

Occipital vein

Posteriorauricular vein

Externaljugular veinVertebral vein

Internaljugular veinSuperior and middle thyroid veinsBrachiocephalicveinSubclavianvein

(a)Superiorvena cava

Veins Of The Right Upper Limb And Thorax Wall

Right subclavian vein

Axillary vein

Brachial veinCephalic veinBasilic vein

Median cubital vein

Median vein of the forearmBasilic vein

Internal jugular veinExternal jugular vein

Left subclavian vein

Superior vena cavaAzygos vein

Inferior vena cava

Ascending lumbar vein

Accessory hemiazygos vein

Hemiazygos vein

Posterior intercostals

Brachiocephalic veins

Ulnar vein

Deep palmarvenous archSuperficial palmarvenous arch

(a)

Digital veins

Cephalicvein Radial vein

Form anastomese frequently

Median cubital vein is used to obtain blood or administer IV fluids

Antecubital Fossa

Figure 19.22

Veins Of The Right Upper Limb And Thoracic Wall

Brachiocephalicveins

Left superiorintercostalvein

Azygos vein

Accessoryhemiazygosvein

Hemiazygosvein

Intercostalveins

Ascendinglumbar vein

Renal vein

Superior venacava

Intercostalveins

(b)

Inferior venacava

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5

6

7

8

9

10

11

12

Lumbar veins Gonadal (testicular or ovarian) veins Renal veins Suprarenal veins Hepatic veins

Veins of the Abdomen

Tributaries Of The Inferior Vena Cava

Rightsuprarenal vein

Rightgonadal vein

Hepatic veins

Inferior vena cava

External iliac vein

Inferior phrenicvein

Renal veins

Lumbar veins

Left ascendinglumbar vein

Left gonadal veinCommon iliac vein

Internal iliac vein

Left suprarenal vein

Dissection of the posterior abdominal wall

Diaphragm

Right Left

Inferiorvena cava

Hepaticveins

Renal veins

Commoniliac veins

Abdominalaorta

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 Pelvis and Lower Limbs

Veins Of The Right Lower Limb And Pelvis

(b)

Popliteal vein

Common iliac vein

Fibular (peroneal)veinAnterior tibial vein

Dorsalis pedis veinDorsal venous archMetatarsal veins

Internal iliac veinExternal iliac veinInguinal ligament

Femoral veinGreat saphenousvein (superficial)

Great saphenous vein

Popliteal veinAnterior tibial veinFibular (peroneal) vein

Small saphenous vein(superficial)Posterior tibial vein

Plantar veins

Plantar archDigital veins

(a)

Flowchart Summarizing The Main VeinsR. External jugular– superficial head and neck

R. vertebral– cervical spinal cord and vertebrae

R. brachiocephalic– R. side of head and R. upper limb

Superior vena cava– runs from union of brachiocephalic veins behind manubrium to R. atrium

Inferior vena cava– runs from junction of common iliac veins at L5 to R. atrium of heart

R. atrium of heart

Diaphragm

L. brachiocephalic– L. side of head and L. upper limb

Intracranialdural sinuses

R. internal jugular– dural sinuses of the brainR. subclavian

– R. head, neck, and upper limb Same as R. brachiocephalic

R. axillary

Azygos system– drains much of thorax

L. and R. hepatic veins– liver

Veins ofL. lower limb

L. and R. renal veins– kidneys

Lumbar veins (several pairs)– posterior abdominal wall

R. suprarenal(L. suprarenal drains into L. renal vein)– adrenal glands

R. gonadal(L. gonadal drains into L. renal vein)– testis or ovary

Veins ofR. lower limb

Veins ofR. upperlimb

R. common iliac– pelvis and R. lower limb

L. common iliac– pelvis and L. lower limb

(a)