CH6 Part I

Chapter 6: Vascular System Overview

General Structure of the Vascular System

• The vascular system consists of:

  • Arterial Blood Supply

  • Capillary Network

  • Venous Drainage

Vascular Plexuses

• A vascular plexus is a large network of blood vessels.

• Contains important venous plexuses in the head and neck.

Anastomosis

• Blood vessels communicate through anastomoses (connecting channels among vessels).

Layers of Blood Vessels

• Blood vessels have three tunics:

  1. Tunica Intima: Inner endothelial layer.

  2. Tunica Media: Middle smooth muscle layer; varies in elastic fibers.

  3. Tunica Externa: Outer connective tissue layer.

Arterial Blood Supply Function

• Arteries carry blood away from the heart.

• Subdivided into three classes based on:

  • Smooth muscle amount

  • Elastic fibers

  • Vessel size and function.

Arterial Structures

• Arterial Branching:

  • Starts large, branches into smaller arteries and arterioles, leading to a capillary network.

  • Arterioles control capillary filling and arterial pressure.

Capillary Network

• Capillaries have smaller diameters and provide blood to tissues through:

  • Oxygen and metabolic waste product exchange.

Venous Drainage

• Veins collect blood from capillaries, larger venules converge into larger veins.

• Veins travel to the heart; have thinner walls and larger luminal diameters than arteries.

• Common misconception that veins in the head lack one-way valves; most do to prevent backflow.

Types of Veins

• Superficial Veins: Located just below the skin.

• Deep Veins: Generally accompany larger arteries, more protected.

• Venous Sinuses: Blood-filled spaces between tissues, interconnected by anastomoses.

Cancer Spread through Blood Vessels

• Blood vessels are less numerous than lymphatic vessels but can spread cancer faster due to their parallel pathways.

Arterial Blood Supply to the Head and Neck

• Major arteries include:

  • Common Carotid

  • Subclavian Arteries

• Different origins for the right and left sides:

  • Left: Arteries begin directly from the aorta.

  • Right: Branch from the brachiocephalic artery.

Common Carotid Artery

• Travels superiorly alongside trachea and larynx.

• Ends by bifurcating into internal and external carotid arteries at the thyroid cartilage level.

• Common carotid sinus provides reliable palpitation point for pulse measurement.

Subclavian Artery

• Begins lateral to the common carotid, primarily supplies the upper extremities.

Internal Carotid Artery

• Travels superiorly with no branches in the neck, supplying intracranial structures and the ophthalmic artery.

External Carotid Artery

• Begins at the termination of the common carotid; has branches supplying tissues in the head and neck.

  • Grouped into anterior, medial, posterior, and terminal branches.

Anterior Branches of External Carotid Artery

• Includes:

  • Superior Thyroid Artery: Supplies the thyroid gland and adjacent structures.

  • Lingual Artery: Supplies suprahyoid muscles and the floor of the mouth.

  • Facial Artery: Supplies several regions in the face with major branches like the ascending palatine, tonsillar branches, and labial arteries.

Medial Branches of External Carotid Artery

• Ascending Pharyngeal Artery: Supplies pharyngeal walls, soft palate, and meninges.

Posterior Branches of External Carotid Artery

• Includes:

  • Occipital Artery: Supplies the posterior scalp and muscles.

  • Posterior Auricular Artery: Supplies the internal ear and mastoid process.

Terminal Branches of External Carotid Artery

• Superficial Temporal Artery: Supplies the temporal region.

• Maxillary Artery: The largest terminal branch; has three parts supplying facial structures.

Maxillary Artery Branches

• First Part: Includes deep auricular, anterior tympanic, middle meningeal, accessory middle meningeal, and inferior alveolar arteries, supplying various regions adjacent to the temporomandibular joint.

• Second Part: Supplies muscles such as temporalis, pterygoid, and masseter.

• Third Part: Enters pterygopalatine fossa; branches supply the palate and nasal cavity.