Blood Vessels and Blood Circulation

Blood Vessels and Blood Circulation

Overview

• Systemic circulation includes arteries and veins with their respective branches.
• Circulation Physiology:
  • Types include pulmonary and systemic circuits.
  • Blood flow dynamics.
  • Blood pressure regulation, determinants, control, and measurement.
• Blood vessels:
  • Types: Arteries, arterioles, capillaries, venules, veins.
  • Structure: Endothelium, smooth muscle, connective tissue.
• Key Vessels:
  • Aorta and its major branches (iliac, carotid, subclavian).
  • Anastomoses.
  • Venae cavae (superior and inferior).
  • Venous sinuses.
  • Hepatic portal system (superior mesenteric, splenic, other tributaries).
• Vascular Disorders:
  • Arterial degeneration.
  • Hemorrhage.
  • Shock.
  • Thrombosis.
  • Varicose veins.

Key Terms

• Aneurysm: A localized, blood-filled balloon-like bulge in the wall of a blood vessel.
• Embolus: A blood clot, air bubble, piece of fatty deposit, or other object that has been carried in the bloodstream to lodge in a vessel and cause an embolism.
• Thrombosis: The formation of a blood clot inside a blood vessel, obstructing the flow of blood through the circulatory system.
• Aorta: The main artery of the body, supplying oxygenated blood to the circulatory system.
• Endarterectomy: Surgical removal of part of the inner lining of an artery, used most often when the artery is narrowed or blocked by plaque.
• Varices (or Varicose Veins): Abnormally swollen, twisted veins.
• Arteriole: A small branch of an artery leading into capillaries.
• Endothelium: The thin layer of cells that lines the interior surface of blood vessels and lymphatic vessels.
• Varicose Vein: A vein that has become enlarged and twisted.
• Arteriosclerosis: The thickening and hardening of the walls of the arteries, occurring typically in old age.
• Hemorrhage: An escape of blood from a ruptured blood vessel, especially when profuse.
• Vasoconstriction: The constriction of blood vessels, which increases blood pressure.
• Artery: A blood vessel that conveys blood from the heart to any part of the body.
• Hypertension: Abnormally high blood pressure.
• Vasodilation: The widening of blood vessels, which decreases blood pressure.
• Baroreceptor: A receptor sensitive to changes in pressure.
• Hypotension: Abnormally low blood pressure.
• Vasomotor: Causing or relating to the constriction or dilation of blood vessels.
• Bulk Flow: The movement of a fluid due to a difference in pressure between two locations.
• Phlebitis: Inflammation of a vein.
• Vein: A blood vessel that conveys blood towards the heart.
• Compliance: The ability of a blood vessel to expand and receive blood.
• Shock: A critical condition brought on by a sudden drop in blood flow through the body.
• Vena Cava: Either of the two large veins that return deoxygenated blood from the body into the heart.
• Capillary: Any of the fine branching blood vessels that form a network between the arterioles and venules.
• Sinusoid: A wide, thin-walled blood vessel similar to a capillary, but having a large irregular lumen.
• Venous Sinus: A blood-filled space between two layers of tissue.
• Elasticity: The ability of a blood vessel to return to its original size after being stretched.
• Sphygmomanometer: An instrument for measuring blood pressure.
• Venule: A very small vein, especially one collecting blood from capillaries.

Overview of Blood Vessels

• Differentiate among the five types of blood vessels with regard to structure and function.
• Compare the pulmonary and systemic circuits relative to location and function.

Systemic Arteries

• Name the four sections of the aorta, and list the main branches of each section.
• Trace the pathway of blood through the main arteries of the upper and lower limbs.
• Define anastomosis, cite its function, and give four examples of anastomoses.

Systemic Veins

• Compare superficial and deep veins, and give examples of each type.
• Name the main vessels that drain into the superior and inferior venae cavae.
• Define venous sinus, and give four examples of venous sinuses.
• Describe the structure and function of the hepatic portal system.

Circulation Physiology (Part 1)

• Explain the forces that affect bulk flow across the capillary wall.
• Discuss mechanisms to control blood flow to different organs and then propel blood back to the heart.
• Describe the negative feedback loop controlling blood pressure.

Circulation Physiology (Part 2)

• Explain how changes in overall blood volume, blood viscosity, and vessel compliance impact blood pressure.
• Explain how blood pressure is commonly measured.

Vascular Disorders

• Discuss six disorders involving the blood vessels.

Case Study

• Based on the opening case study, discuss the dangers of thrombosis, and describe one approach to its treatment.

Word Anatomy

• Show how word parts are used to build words related to the blood vessels and circulation.

The Vascular System

• A closed system of vessels that transports blood to and from the lungs and body tissues.

Blood Vessel Types

Blood Circuits

• The pulmonary circuit
  • Pulmonary trunk and its branches
  • Capillaries in lungs
  • Pulmonary veins
• The systemic circuit
  • Aorta
  • Systemic arteries
  • Systemic capillaries
  • Systemic veins

Blood Vessel Structure

• Vessels contain up to three tunics (coats).
  • Inner (endothelium)
    • All vessels
  • Middle (smooth [voluntary] muscle)
    • Controlled by the autonomic nervous system
    • Thinner in veins
    • All vessels except capillaries
  • Outer (supporting connective tissue)
    • All vessels except capillaries.
    • Capillaries have an outer basement membrane.

Compliance and Elasticity

• Compliance: ability of a vessel to expand and receive blood
• Elasticity: ability of a vessel to return to its original size after stretching

Systemic Arteries

• Name the four sections of the aorta, and list the main branches of each section.
• Trace the pathway of blood through the main arteries of the upper and lower limbs.
• Define anastomosis, cite its function, and give four examples of anastomoses.

The Aorta

• Largest artery.
• Receives blood from the left ventricle.
• Branches supply all organs.
• Divided into four segments
  • Ascending aorta
  • Aortic arch
  • Thoracic aorta
  • Abdominal aorta

Aortic Branches

• Ascending Aorta
  • Left and right coronary arteries
• Aortic Arch
  • Brachiocephalic artery
    • Right subclavian artery
    • Right common carotid artery
  • Left common carotid artery
  • Left subclavian artery
• Descending Aorta
  • Branches to the chest wall, esophagus, and bronchi
  • Intercostal arteries

Branches of the Abdominal Aorta

• Unpaired Branches
  • Celiac trunk
    • Left gastric artery
    • Splenic artery
    • Hepatic artery
  • Superior mesenteric artery
  • Inferior mesenteric artery
• Paired Lateral Branches
  • Superior and inferior phrenic arteries
  • Renal arteries
  • Gonadal arteries (ovarian and testicular arteries)
  • Lumbar arteries

Iliac Arteries

• Internal iliac arteries
• External iliac arteries
  • Femoral artery
    • Popliteal artery
      • Tibial arteries
      • Dorsalis pedis

Arteries Supplying the Arm and Head

• External carotid artery
• Internal carotid artery
• Subclavian artery
  • Vertebral artery
  • Axillary artery
    • Brachial artery
      • Radial artery
      • Ulnar artery

Anastomoses

• Communications between two vessels
• Examples
  • Cerebral arterial circle (circle of Willis)
  • Superficial palmar arch
  • Mesenteric arches
  • Arterial arches

Systemic Veins

• Compare superficial and deep veins, and give examples of each type.
• Name the main vessels that drain into the superior and inferior venae cavae.
• Define venous sinus, and give four examples of venous sinuses.
• Describe the structure and function of the hepatic portal system.

Systemic Veins

• Superficial veins
  • Close to body surface
  • Do not accompany arteries
  • Upper limb: cephalic, basilic, median cubital veins
  • Lower limb: saphenous veins
• Deep veins
  • Often named after nearby arteries
  • Lower body: paired femoral and iliac veins
  • Upper body: paired brachial, axillary, subclavian, brachiocephalic, jugular veins

The Venae Cavae and Their Tributaries

• Superior vena cava
  • Head, neck, upper extremities
  • Azygos vein
    • Chest wall
• Inferior vena cava
  • Right, left veins from paired parts, organs
  • Unpaired veins from the spleen, digestive tract

Venous Sinuses

• Large Channels Draining Oxygen-Poor Blood
  • Coronary sinus drains heart muscle.
  • Cranial venous sinuses drain brain; receive CSF.
    • Each sinus drains nearby brain regions.
    • Superior sagittal sinus drains into confluence of sinuses.
    • Inferior sagittal sinus drains into straight sinus, which drains into the confluence of sinuses.
    • Transverse (lateral) sinuses drain confluence of sinuses, empties into internal jugular vein.

Hepatic Portal System

• Portal System: Blood passes through two capillary beds.
  • Carries blood from abdominal organ capillaries to specialized liver capillaries (sinusoids)
  • Hepatic portal vein drains blood from the:
    • Superior mesenteric vein
    • Splenic vein (drains part of the stomach as well)
    • Gastric, pancreatic, inferior mesenteric veins

Circulation Physiology (Part 1)

• Explain the forces that affect bulk flow across the capillary wall.
• Discuss mechanisms to control blood flow to different organs and then propel blood back to the heart.
• Describe the negative feedback loop controlling blood pressure.

Capillary Exchange

• Oxygen, nutrients pass from blood into interstitial (tissue) fluid, and then into cells
• Carbon dioxide, wastes, and synthesized substances move from cells into interstitial fluid and then blood.

Capillary Exchange Processes

Controlling Blood Distribution

• Total blood volume is limited, so blood is diverted from other organs.

Return of Blood to the Heart

• Mechanisms that promote blood’s return to the heart
  • Contraction of skeletal muscles
  • Valves in the veins
  • Breathing

Circulation Physiology (Part 2)

• Explain how changes in overall blood volume, blood viscosity, and vessel compliance impact blood pressure.
• Explain how blood pressure is commonly measured.

Blood Pressure

• Force exerted by blood against vessel walls
• Tightly controlled by a negative feedback loop
• Determined by
  • Total blood volume
  • Cardiac output
  • Resistance to blood flow
  • Blood vessel compliance and elasticity

Pulse Beat

• Pulse beat can be sensed in superficial arteries.
• Result of left ventricular contraction.
• Wave of increased pressure.
• Begins at heart and travels to arteries.
• Indicative of heart rate.

Determinants of Arterial Blood Pressure

• Arterial blood volume
  • Influenced by total blood volume
    • For example, hemorrhage reduces total blood volume and reduces blood pressure
  • Also subject to short-term regulation (next)
• Blood viscosity
  • Elevated hematocrit increases viscosity and BP.
• Vessel compliance
  • For example, atherosclerosis reduces compliance and increases BP

Short-Term Regulation of Blood Pressure: Cardiac Output

• Cardiac output = heart rate (HR) x stroke volume (SV)
• Example: 60 beats per minute (bpm) x 100 mL/beat = 6000 mL/minute

Short-Term Blood Pressure Regulation

• Sensors: Baroreceptors
• Regulated variable: ↓ Blood BP
• Corrects Signals:
  • Cardiovascular Control Center
  • ANS Signals
• Effectors/Effector Actions:
  • Heart: ↑ HR and SV
  • Vessels: vasoconstriction

Blood Pressure Measurement

• Pressure is measured in the brachial artery using a sphygmomanometer.
  • Systolic pressure
    • Occurs during heart contraction
    • Normal systolic: 120 mm Hg
  • Diastolic pressure
    • Occurs during heart relaxation
    • Normal diastolic: 80 mm Hg

Abnormal Blood Pressure

• Hypotension
  • Lower than normal blood pressure
• Hypertension (high blood pressure)
  • Kidney disease
  • Endocrine disorders
  • Arterial disease
  • Tumors
• Essential hypertension
  • No apparent medical cause

Treatment of Hypertension

• Established guidelines
  • Prehypertension (120/80–139/89)
    • Lifestyle modifications
  • Hypertension (over 140/90)
    • Drug therapy and lifestyle modifications

Vascular Disorders

• Arterial degeneration
  • Arteriosclerosis
• Aneurysm
• Hemorrhage
• Shock
  • Types of shock (cardiogenic, septic, hypovolemic, anaphylactic)
• Thrombosis
• Varicose veins

Atherosclerosis

• Plaque deposits within arterial walls, leading to narrowing and hardening of the arteries.

Cerebral Aneurysm

• Bulging sac in a blood vessel in the brain, posing a risk of rupture and hemorrhage.

Varicose Veins

• Twisted and enlarged veins, commonly occurring in the legs, due to weakened valves.

Case Study: Thrombosis

• Hereditary protein S deficiency may cause blood to clot more easily.
• Deep vein thrombosis (DVT) can cause phlebitis.
  • Signs: Pain, redness, swelling, pulmonary embolus (blood clot breaks loose and travels to the lung causing shortness of breath, chest pain, cough, or fainting)
  • Daily injections and/or oral doses of anticoagulant medication until the clot is resolved
  • Frequent laboratory tests to adjust the dose of anticoagulants
• Supportive treatment: Compression stocking and hourly activity of sitting for prolonged periods.
• No menopausal hormone therapy for women.
• No hormonal contraceptives for women if they test positive for the genetic trait.

Word Anatomy