A&P 2 Lab exam 2

Blood Vessel Structure

• Blood Vessel Walls Layers:

  • Composed of three layers (tunics):

    • Tunica Interna (Intima):

      • Innermost layer in contact with blood.

      • Comprises endothelium (simple squamous epithelium), a basement membrane, and connective tissue.

      • Functions:

        • Minimizes friction for smooth blood flow.

        • Regulates exchange of materials.

      • Veins: endothelial folds create valves preventing backflow.

      • Capillaries: composed only of the tunica interna.

    • Tunica Media:

      • Middle layer, primarily smooth muscle with elastic fibers.

      • Responsible for vasoconstriction (narrowing) and vasodilation (widening) of vessels; collectively called vasomotion.

      • Arteries have a thicker tunica media allowing them to withstand higher blood pressures than veins.

      • Elastic laminae present in some vessels.

    • Tunica Externa (Adventitia):

      • Outermost layer made of loose areolar connective tissue.

      • Anchors vessels to surrounding structures.

      • Vaso vasorum: small blood vessels supplying larger vessel walls.

Artery vs. Vein

• Arteries:

  • Thick walls with a prominent tunica media.

  • Maintain a round lumen, can manage high pressure.

• Veins:

  • Thinner walls; may collapse when cut.

  • Operate under low pressure and contain valves.

Blood Oxygenation

• Deoxygenated Blood (Blue):

  • Lower oxygen saturation (around 75% when returning to the heart).

  • Appears bluish through vein walls due to darker deoxygenated hemoglobin.

  • Associated vessels:

    • Systemic veins, right atrium, right ventricle, pulmonary trunk, pulmonary arteries.

• Oxygenated Blood (Red):

  • Achieves around 98% oxygen saturation after gas exchange in lungs.

  • Bright red due to oxygenated hemoglobin.

  • Associated vessels:

    • Pulmonary veins, left atrium, left ventricle, systemic arteries.

General Function of Arteries

• Carry blood away from the heart.

Types of Arteries

• Conducting (Elastic) Arteries:

  • Largest arteries, handle high-pressure blood flow.

  • Contain internal and external elastic laminae allowing expansion during systole and recoil to maintain blood flow.

  • Examples include the aorta and pulmonary trunk.

• Muscular (Distributing) Arteries:

  • Medium-sized, branch from conducting arteries.

  • Distribute blood to specific organs and tissues, with more smooth muscle and fewer elastic fibers.

• Small Arteries and Arterioles:

  • Smallest arteries, modulate blood flow into capillary networks.

  • Grant priority of blood flow according to tissue metabolic needs.

Capillary Structure and Function

• Capillaries:

  • Microscopic vessels branching from arterioles.

  • Precapillary sphincters control blood flow.

  • Allow exchange of nutrients and gases primarily through simple diffusion.

  • Types of Capillaries:

    • Continuous Capillaries:

      • Most common, with endothelial cells connected by tight junctions and small intercellular clefts; allow small solute passage.

      • These tight junctions form the blood-brain barrier.

    • Sinusoidal Capillaries:

      • Have larger clefts; allow larger substances such as blood cells and proteins.

      • Found in liver, bone marrow, and spleen.

    • Fenestrated Capillaries:

      • Comprise both clefts and fenestrations; facilitate rapid filtration in digestive and kidney systems.

Venous System Structure

• Venules and Veins:

  • Venules drain capillary beds; converge into medium veins.

  • Medium veins merge into large veins (e.g., superior and inferior vena cava).

  • Veins function as capacitance vessels, storing excess blood.

Mechanisms of Venous Return

• Skeletal Muscle Pump:

  • Muscle contraction compresses veins pushing blood toward the heart.

• Venous Valves:

  • Prevent backflow during muscle relaxation.

• Respiratory Pump:

  • Changes in thoracic pressure during breathing assist venous return.

• Cardiac Suction:

  • The cohesive nature of blood assists return to the heart, aided by arterial expansion during systole.

Major Arteries and Veins Near the Heart

• Arteries:

  • Aorta branches post-coronary circulation into:

    • Brachiocephalic trunk, left common carotid artery, left subclavian artery.

  • Pulmonary trunk carrying deoxygenated blood to the lungs.

• Veins:

  • Superior vena cava (drains upper body) and inferior vena cava (drains lower body).

  • Pulmonary veins return oxygenated blood from the lungs to the heart.

Head Circulation

• Arteries:

  • Common carotids branch into internal and external carotids, supplying face and brain.

  • Vertebral arteries supplying parts of the brain.

• Veins:

  • External jugulars drain external head structures.

  • Internal jugulars drain cranial cavity.

Trunk and Limb Circulation

• Arteries:

  • Thoracic aorta to abdominal aorta, branching into common iliac arteries.

• Veins:

  • Femoral veins transitioning into external and internal iliac veins.

  • Common iliac veins merging into the inferior vena cava.

Arterial Supply to Head and Neck

• Internal Carotid Arteries: supply deep skull and brain.

• External Carotid Arteries: branch to supply face and scalp.

• Vertebral Arteries: branch from subclavian arteries to supply posterior head.

Venous Drainage from Head and Neck

• Dural Venous Sinuses: drain brain and empty into internal jugular vein.

• Facial and Superficial Temporal Veins: merge into the internal jugular vein.

• Occipital Vein: drains into the external jugular vein which merges with the subclavian vein.

Key Vessels and Pulse Points

• Identification of arterial pulse points includes common carotid, superficial temporal, and facial arteries.

Arterial Supply to the Brain

• Internal Carotid Arteries: Branch into middle cerebral and anterior communicating arteries for anterior brain supply.

• Vertebral Arteries: posterior brain supply; merge into basilar artery which branches into posterior cerebral arteries.

• Circle of Willis: allows collateral circulation at the brain base connecting anterior and posterior blood supplies.

Venous Drainage from the Brain

• Cerebral Veins: drain brain tissue.

• Dural Venous Sinuses: receive blood from cerebral veins, emptying into internal jugular vein.

Pulmonary Arteries

• Pulmonary trunk branches into right and left pulmonary arteries to carry deoxygenated blood to lungs.

  • Carry blood to alveoli for gas exchange.

Arteries of the Abdomen

• Abdominal Aorta: branches into several key arteries:

  • Celiac Trunk, Superior Mesenteric Artery, Renal Arteries, Gonadal Arteries, Inferior Mesenteric Artery, Common Iliac Arteries.

Veins of the Abdomen

• Inferior Vena Cava formed by merging common iliac veins receiving blood from important veins - renal, hepatic, and gonadal veins.

Key Points

• Hepatic Portal System: drains blood from digestive organs to the liver for nutrient-processing, involving two sets of capillary beds.

Pulmonary Veins

• Four pulmonary veins return oxygenated blood to the left atrium of the heart.

Arterial Supply to the Lower Limb

• External Iliac Artery: supplies the lower limb transitioning to the femoral artery.

• Femoral Artery: key pulse point; branches to popliteal and further down.

• Popliteal Artery: gives rise to anterior tibial, posterior tibial, and fibular arteries.

Venous Drainage of the Lower Limb

• Deep and Superficial Veins: include major pathways for blood return from the legs to the heart, merging at different points to form the external iliac vein.

Blood Pressure (BP)

• Definition: Force exerted by blood against vessel walls.

• Components: Systolic (peak) and diastolic (minimum) pressures.

• Measurement: BP expressed as systolic/diastolic (mm Hg).

Functions of the Lymphatic System

• Fluid Recovery: Returns interstitial fluid to bloodstream, preventing edema.

• Lipid Absorption: Absorbs lipids via lacteals.

• Immunity: Provides both nonspecific and specific immune responses.

Components of the Lymphatic System

• Lymphatic Vessels: transport lymph, including capillaries, collecting vessels, trunks, and ducts.

• Lymph Nodes: filter lymph and serve as immune responses.

• Other Organs: Thymus (T-cell maturation), spleen (filters blood), and tonsils (protect from pathogens).

Lymphatic Fluid (Lymph)

• Comprised of interstitial fluid entering lymphatic capillaries.

Immunity

• Nonspecific Resistance: Defenses like physical barriers and phagocytes.

• Specific Immunity: Lymphocytes providing tailored immune responses.

Lymph Flow

• Aided by mechanisms like muscle pumps, thoracic pump.

Respiratory System Overview

• Functional Divisions:

  • Conducting Zone: airways for movement (from nose to bronchioles).

  • Respiratory Zone: gas exchange sites.

Key Structures and Functions of Respiratory System

• Nasal Cavity: warms, filters, and moistens air. Contains olfactory epithelium for smell.

• Pharynx: pathway for air, divided into nasopharynx, oropharynx, laryngopharynx.

• Larynx: voice box housing vocal cords.

• Trachea: conveys air, contains C-shaped cartilaginous rings.

• Bronchial Tree: branching from trachea into bronchi and bronchioles.

• Lungs: lobed structures facilitating gas exchange, surrounded by pleura.

Mechanics of Breathing

• Inhalation and Exhalation: involve muscle contraction and relaxation, governed by pressure changes.

Lung Volumes and Capacities**

• Tidal Volume (TV): volume of normal breath.

• Inspiratory/Expiratory Reserve Volumes (IRV/ERV): additional inhaled/exhaled air.

• Residual Volume (RV): air remaining post-exhalation.

• Vital Capacity (VC): measure of total exchangeable air.

• Minute Respiratory Volume (MRV): total air breathed in a minute.

Neural Control of Breathing

• Neural Centers: pons and medulla integrate sensory input.

• Chemoreceptors monitor blood levels of CO2 and O2, influencing respiratory rate.