cardiovascular

Learning Objectives – Blood Vessels

  • Compare and contrast the anatomical structure of:

    • Arteries

    • Arterioles

    • Capillaries

    • Venules

    • Veins

  • Compare and contrast the functional differences of:

    • Arteries

    • Arterioles

    • Capillaries

    • Venules

    • Veins

  • Label the major blood vessels of the pulmonary and systemic circulations

  • Identify and describe the hepatic portal system

Overview of Circulatory Pathways

Systemic Circulation

  • Function: Transport of blood to head, arms, legs, and trunk

Pulmonary Circulation

  • Function: Transport of blood to lungs

Key Blood Vessels

  • Pulmonary artery

  • Lungs

  • Pulmonary vein

  • Vena cava

  • Aorta

  • Hepatic vein

  • Renal vein

  • Liver

  • Hepatic artery

  • Hepatic portal vein

  • Stomach, intestines

  • Renal artery

  • Kidneys

  • Upper body

  • Lower body

Blood Flow Directions

  • Vessels transporting oxygenated blood

  • Vessels transporting deoxygenated blood

  • Vessels involved in gas exchange

Arteries and Their Structure

Functions and Characteristics

  • Arteries carry blood away from the heart

  • Capillaries engage in exchange of oxygen with tissues

  • Veins return blood to the heart

Physical Characteristics of Arteries

  • Arteries receive high-pressure blood from the heart

  • Structural Features:

    • Thick muscular walls

    • Highly elastic to allow expansion and recoil

    • More rounded appearance with smaller lumen (central canal)

Arterial Layers

  • Tunica Externa:

    • Protective outer layer composed of collagen fibers

  • Tunica Media:

    • Thick layer made of smooth muscle

  • Tunica Intima:

    • Smooth and elastic inner surface

Changes in Artery Walls

  • Wall structure changes as arteries move further from the heart:

    • Elastic Arteries:

    • Largest and nearest to the heart

    • Contains many elastic fibers to resist stretching when the heart pumps

    • Muscular Arteries:

    • Medium-sized with a muscular tunica media to maintain blood pressure

    • Arterioles:

    • Smallest arteries that slow down blood and reduce pressure before reaching capillaries

Capillaries

Functionality

  • Site of oxygen exchange

  • Structural Features:

    • Small gaps in the lining of the tunica intima allow for oxygen exchange

    • Fenestrations: Allow passage of larger molecules (hormones, nutrients)

    • Intercellular Gaps: Allow passage of white blood cells

  • Capillary diameter:

    • Approximately 5-10 micrometers

Vein Structure and Function

Characteristics of Veins

  • Veins receive low-pressure blood from capillaries

  • Structural Features:

    • Thinner and less muscular walls that can flatten

    • Valves to prevent backflow of blood

    • Larger lumen to hold greater volumes of blood

Changes in Vein Structure

  • As blood approaches the heart, vein structure changes:

    • Large Veins:

    • Thickest walls and largest lumen (e.g., Inferior and Superior Vena Cava)

    • Medium-Sized Veins:

    • Slightly thinner walls, contain valves to prevent backflow

    • Venules:

    • Extremely small veins that collect blood from capillaries

Mechanics of Venous Return

  • Skeletal muscles aid the return of blood to the heart

  • Gravity can impede venous return without assistance

    • Skeletal muscles surrounding veins help pump blood against gravity

    • Valves prevent the backflow of blood

Chronic Venous Insufficiency

Definitions and Implications

  • Chronic Venous Insufficiency: A condition characterized by inadequate venous blood flow

    • Normal venous blood flow: Deteriorated by valve failure

    • Results in blood pooling and increased pressure

    • Can lead to venous hypertension, causing capillary damage and edema

    • Prolonged hypertension can trigger formation of venous leg ulcers

Discussion Prompt

  • Consider the brain's requirement for constant blood supply:

    • Why do we occasionally feel dizzy after standing up from a seated or lying position?

Pulmonary Circulatory Pathway

  • Sequence of blood flow:

    • Superior/Inferior Vena Cava

    • Right Atrium

    • Right Ventricle

    • Pulmonary Arteries

    • Pulmonary Veins

  • Additional Structures:

    • Ascending aorta, Right lung, Right pulmonary arteries, Right pulmonary veins, aortic arch, pulmonary trunk, Left lung, Left pulmonary arteries, Left pulmonary veins, pulmonary capillaries, descending aorta

Systemic Pathway Complexity

  • Systemic pathway is more complex than the pulmonary pathway covering multiple branches:

    • Vertebral, Right subclavian, Brachiocephalic trunk, Thoracic aorta, and more

  • Key Branches:

    • Aortic arch leads to several important arteries including the celiac trunk and various iliac arteries

Major Branches of the Aorta

Aortic Arch

  • Comprises 3 main branches:

    1. Brachiocephalic

    • Supplies right subclavian and right common carotid

    1. Left Common Carotid

    2. Left Subclavian

  • Important Terms:

    • Brachio- means “arm” and cephalic means “head”

    • Sub- means “below” and clavian refers to the “clavicle”

Abdominal Branches of the Aorta

  • Celiac Trunk: Supplies blood to the liver, stomach, spleen, gallbladder, pancreas

  • Superior/Inferior Mesenteric Arteries: Supplies blood to the intestines

Inferior Branches of the Aorta

  • Aorta divides into left and right common iliac arteries

  • Each common iliac artery further divides into internal and external iliac arteries

Major Leg Arteries

  • Follow musculoskeletal naming conventions:

    • Femoral Artery

    • Leads to Popliteal Artery (at the posterior knee)

    • Branches into Tibial/Fibular Arteries

    • Multiple branches include anterior tibial, posterior tibial, peroneal, etc.

Major Arm Arteries

  • Follow similar conventions to leg arteries:

    • Subclavian: Located below the clavicle

    • Axillary: Located in the armpit

    • Brachial: Upper arm

    • Branches to Radial and Ulnar, then leads to Palmar and Digital arteries

Blood Supply to the Head/Neck/Brain

Key Arteries

  • Internal Carotid: Supplies blood to the brain

  • External Carotid: Supplies blood to the outer head and face

  • Vertebral Artery: Supplies blood to the posterior neck and spinal cord, passes through the transverse foramen of cervical vertebrae

Circle of Willis

  • An arterial loop in the brain providing redundancy in case of blockages

Major Branches Include:

  • Anterior Cerebral: Supplies the frontal lobe

  • Middle Cerebral: Supplies the temporal and parietal lobes

  • Posterior Cerebral: Supplies the occipital lobe and brainstem

Carotid Artery Injuries in Contact Sports

  • Notable cases:

    • Clint Malarchuk (1989)

    • Richard Zednik (2008)

  • Highlight: Arteries operate under high pressure, potentially leading to arterial spray upon injury, compared to veins that exhibit low pressure leading to constant oozing

Naming Conventions for Veins

  • Follow similar naming conventions to arteries, e.g.,

    • External Jugular, Subclavian, Axillary, Brachial, Cephalic, etc.

  • Inferior Vena Cava: Returns blood from abdomen and legs

  • Superior Vena Cava: Returns blood from head, neck, and arms

Major Vein Pathways

  • Internal Jugular Vein: Returns blood from brain, temporal and facial regions

  • External Jugular Vein: Returns blood from the posterior head

  • Venous Return from Arm: Subclavian vein receives blood from several arm veins including Axillary and Cephalic

Lower Limb Venous Return

  • Lower limb veins flow back to the common iliac vein:

    • External Iliac, Femoral, Popliteal, Tibial/Fibular, Digital, Great Saphenous, etc.

Hepatic Portal System

  • The liver is essential for filtration and metabolic processes

  • Portal Vein: Connects two capillary beds allowing nutrient-rich blood from the digestive tract to the liver for processing

  • Hepatic derives from the Greek word for liver

Role of the Circulatory System in Other Anatomical Systems

  • Endocrine: Distributes hormones

  • Muscular: Delivers nutrients and oxygen

  • Skeletal: Delivers calcium for bone formation

  • Digestive: Absorbs nutrients and water

  • Reproductive: Supports reproductive functions in genitalia

  • Urinary: Delivers blood to kidneys to filter waste

  • Lymphatic/Immune: Transports white blood cells

  • Integumentary: Distributes platelets to injured tissue