Anatomy of Arteries and Veins Quiz

Course Information

• Academic Year: 2024-2025
• Year: 1
• Semester: 1
• Module: Blood and Body Fluids (BLF) 103

Lecture 1: Blood & Lymphatic Vessels

• Topic: Circulatory System
• Objectives: Outline general microscopic structure of blood vessels, describe microscopic structure of different types of arteries and veins, compare between medium-sized arteries and veins, classify types of arteriovenous connections, describe histological features of different types of blood capillaries, recognize histological criteria of lymphatic vessels and capillaries, and compare between the histological structure of blood and lymphatic capillaries.

Introduction

• Circulatory System: Divided into Blood vascular system (Cardiovascular system) and Lymphatic vascular system.
• Components: Heart, Blood vessels, Lymphatic capillaries, and Lymphatic vessels.

Types of Blood Vessels

• Arteries:
  • Large (elastic) artery
  • Medium (muscular) artery
  • Small artery
• Veins:
  • Large vein
  • Medium vein
  • Small vein
• Arteriovenous connections

General Structure of Blood Vessels Wall (Except Capillaries)

• Tunica Intima: Innermost layer, in contact with blood.
• Tunica Media: Middle layer.
• Tunica Adventitia: Outermost layer.

Tunica Intima

• Consists of: Endothelium (simple squamous epithelium), Subendothelial CT (thin layer of loose connective tissue).
• Internal Elastic Lamina: Sheet of elastin separating tunica intima from tunica media.

Tunica Media

• Consists of: Smooth muscle cells, Elastic fibers, and Proteoglycans.
• External Elastic Lamina: Separates tunica media from tunica adventitia.

Tunica Adventitia

• Consists of: Collagen fibers, Fibroblasts, Vasa vasorum (vessels of the vessel), and Nervi vasorum (vasomotor nerves).

Vasa Vasorum & Nervi Vasorum

• Vasa vasorum: Arterioles, capillaries, and venules in tunica adventitia, provide nutrients and remove waste products. More numerous in veins.
• Nervi vasorum: Network of autonomic nerve fibers, control contraction of smooth muscle. More prominent in arteries.

Arterioles

• Diameter: < 0.1 mm (10-100 µm)
• Tunica Intima: Endothelium, very thin subendothelial layer, no internal elastic lamina.
• Tunica Media: 1-3 layers of smooth muscle cells.
• Tunica Adventitia: Very thin.
• Functions: Control blood flow to capillaries, major determinants of systemic blood pressure

Arteriovenous Anastomoses (AV Shunts)

• Definition: Direct routes between arterioles & venules bypassing capillaries.
• Structure: Initial arterial segment, intermediate segment (thicker tunica media acting as a sphincter, thicker tunica adventitia acting as a capsule, richly innervated by autonomic fibers), terminal venous segment (typical of a postcapillary venule).
• Sites: Skin of fingertips, nose, lips, and erectile tissue.
• Mechanisms: Closed shunt - blood flows through capillary bed, Open shunt - blood bypasses capillary bed.

Capillaries

• Structure: Single layer of endothelial cells resting on basal lamina, surrounded by pericytes.
• Function: Metabolic exchange between blood and surrounding tissues.
• Adaptations: Thin walls, extensive surface area, slow pulsatile blood flow.
• Types:
  • Continuous capillaries: Common type, found in connective tissue and muscle tissues.
  • Fenestrated capillaries: More permeable, found in areas engaged in fluid transport and secretion, such as kidneys, intestine, and endocrine glands.
  • Sinusoidal capillaries: Highly permeable, found in liver, bone marrow, and spleen.

Lymphatic Vascular System:

• Function: Drains excess interstitial fluid (lymph) from tissue spaces and returns it to the blood.
• Lymphatic capillaries:
  • Networks close to blood capillaries, blind-ended tubes, formed of single layer of endothelial cells.
  • Basal lamina is discontinuous.
  • Anchoring filaments prevent collapse of lumen.
  • More permeable than blood capillaries.

Lymphatic Vessels:

• Structure: Endothelial cells joined by tight junctions, basal lamina is continuous, valves, smooth muscle and connective tissue, lymph nodes.
• Function: Transport lymph, immune cells.
• Pathway: Vessels converge into trunks (thoracic duct and right lymphatic duct).

Summary

• Blood vessels: Composed of tunica intima, media, and adventitia.
• Aorta: Thickest tunica media.
• Muscular arteries & veins characteristics listed.
• Capillary types described: Continuous, Fenestrated, Sinusoidal.
• Lymphatic system components and function outlined.
• Overview of Arteriovenous (AV) anastomoses.

Interactive Questions (Examples)

• Large elastic arteries: Identify false statement regarding their structure.
• Sinusoidal capillaries: Identify a characteristic.
• Fenestrated capillaries: Identify their two types.