Anatomical Considerations

Anatomical Considerations

Introduction

  • Surface Features: Before conceptualizing the internal anatomy of the body, familiarity with the surface features is essential. Understanding surface anatomy aids in inferencing underlying structures.

  • Anatomical Position Reference: The body is always referred to in the anatomical position.

  • Veins vs. Arteries: For linear guides or anatomical limits regarding veins, remember the blood flow direction is opposite that of arteries: veins flow in reverse.

Definitions

  • Anatomical Guide: Method of locating a structure by reference to an adjacent known or prominent structure.

  • Linear Guide: A line drawn or visualized on the skin's surface representing the approximate location of deeper structures.

  • Anatomical Limit: Point of origin and termination of a structure concerning adjacent structures.

Common Carotid Artery & Internal Jugular

  • **Body Identification Features: *Be familiar with the following anatomical landmarks:*

    • Clavicle

    • Mandible

    • Angle of the jaw

    • Mastoid Process of the Temporal Bone

    • Hyoid Bone

    • Sternum

    • Sternoclavicular Articulation

    • Suprasternal Notch

    • Thyroid Cartilage of the Larynx

    • Sternocleidomastoid Muscle (SCM)

    • Platysma Muscle

    • Observable as shallow, transverse wrinkles of the neck

Anterior Triangle of the Neck

  • Triangle Definition: A line runs along the middle of the neck from the tip of the mandible to the sternum and extends along the anterior border of the SCM and lower margin of the mandible.

  • Palpation Points: In the triangle's midline, you can palpate the hyoid bone and thyroid/cricoid cartilages.

  • Superficial Vessels: The vessels of the neck are very superficial unless the platysma muscle is incised through, then the vessels become visible.

  • SCM Attachment: The sternocleidomastoid muscle attaches to both the Mastoid Process and the Manubrium of the sternum, with the external jugular vein being identifiable on its surface.

  • Carotid Sheath Position: Lying posterior and parallel to the SCM; Within the sheath:

    • The carotid artery is medial (toward the midline)

    • The internal jugular vein is lateral

    • The vagus nerve is located between both.

Right Common Carotid

  • Anatomical Guide: Located posterior to the medial border of the sternocleidomastoid muscle on their respective neck sides.

  • Linear Guide: From the respective sternoclavicular articulation to a point over respective earlobes.

  • Anatomical Limit: Level of the right sternoclavicular articulation, extending to the superior border of the thyroid cartilage.

  • Origin: The right common carotid artery is a terminal branch of the brachiocephalic artery.

  • Artery-Vein Relationship: The artery is deep and medial to the vein, which is superficial and lateral.

  • Branches: The right common carotid has no branches and terminates at bifurcation into the right internal and external carotid arteries.

Left Common Carotid

  • Anatomical Guide: Located posterior to the medial border of the sternocleidomastoid muscle on the neck’s respective side.

  • Linear Guide: From the respective sternoclavicular articulation to a point over respective earlobes.

  • Anatomical Limit: Level of the 2nd costal cartilage to the superior border of the thyroid cartilage.

  • Origin: It is a branch off the Arch of the Aorta.

  • Artery-Vein Relationship: The artery is deep and medial to the vein, with the vein being superficial and lateral.

  • Branches: Like the right, the left common carotid has no branches and terminates at bifurcation into the left internal and external carotid arteries.

Common Carotid Branches

  • External Carotid Branches:

    • Ascending Pharyngeal

    • Superior Thyroid

    • Lingual

    • Facial

    • Occipital

    • Posterior Auricular

    • Maxillary

    • Superficial Temporal

  • Internal Carotid Branches:

    • Branches arise within the Carotid Canal

    • Ophthalmic

    • Anterior Cerebral

    • Middle Cerebral

    • Posterior Communicating

    • Choroidal

Facial Artery

  • Considerations for Usage: Sclerotic conditions can occlude the common carotid artery, limiting arterial solutions to facial tissues. Certain pathological conditions or injuries might deem this artery unsuitable for injection.

  • Alternative Approach: The facial artery is selected for access to frontal facial structures, particularly lips and superficial tissues.

  • Incision Location: Made along the inferior border of the mandible, just anterior to the angle of the jaw; it's superficial, requiring a small incision and reduced diameter arterial tube.

  • Sealing Incision: Post-injection, use adhesive instead of suture for optimal concealment.

Axilla

  • Shape Description: With the arm extended (abducted), the axilla resembles a truncated pyramid.

Borders of Axilla

  • Ribs and Intercostals: Anterior and posterior axillary folds.

  • Significant Structures: Contains six branches of the axillary artery, typically large.

Anterior Fold

  • Identification: Grasp tissue on the contralateral side; contains pectoralis major & minor, and subclavius.

Posterior Fold

  • Identification: Grasp tissue on the posterior side of the axilla; consists of the latissimus dorsi, subscapularis, and teres major muscles.

Medial Wall

  • Components: Ribs 2-6 and their intercostal muscles covered by the serratus anterior, which is visible on very lean individuals.

Lateral Wall

  • Components: The shaft of the humerus, biceps brachii, and coracobrachialis. The coracobrachialis is visible only in muscular individuals.

Cervicoaxillary Canal

  • Definition: Apex of the axilla, bordered by the clavicle, scapula, and 1st rib; the 1st rib is often difficult to feel.

Base of the Axilla

  • Description: Dome-shaped fascia and skin over which hair is found. The axillary sheath contains key structures that transit from neck to axilla.

Brachial Plexus

  • Composition: Made up of three nerves: medial, lateral, and posterior, grouped around the artery.

Access Challenges

  • Accessing the axillary artery can be difficult due to surrounding nerves and structures.

Axillary Artery

  • Anatomical Guide: Behind the medial border of the coracobrachialis muscle.

  • Linear Guide: From the center of the axillary space to the center of the base's lateral border, parallel to the arm's long axis.

  • Anatomical Limit: Lateral border of the first rib to the inferior border of the teres major muscle.

  • Origin: Continuation of the subclavian artery.

  • Artery-Vein Relationship: Artery is lateral and deep to the vein, while the axillary vein is superficial and medial.

  • Branches: Includes thoracic artery, thoracoacromial artery, lateral thoracic artery, subscapular artery, anterior humeral circumflex artery, and posterior humeral circumflex artery.

Brachial Artery

  • Anatomical Guide: Located at the bicipital groove at the posterior margin of the medial border of the biceps brachii muscle.

  • Linear Guide: From the center of the base of the axillary space to a point about 1 inch below the elbow's front.

  • Anatomical Limit: From the inferior border of the teres major tendon to a point inferior to the antecubital fossa.

  • Origin: The continuation of the axillary artery.

  • Artery-Vein Relationship: The artery is lateral and deep to the vein, while the basilic vein is medial and superficial to it.

  • Incision: Made along the upper third of the linear guide.

Distal Forearm

  • Arteries Present: Contains radial and ulnar arteries with the radial on the lateral side and the ulnar on the medial side,

  • Anatomical Position Reference: In the anatomical position, hands face out, positioning the radial artery nearest to the thumb.

Radial Artery

  • Key Identification Features: Between the styloid process and the flexor carpi radialis muscle on the anterior surface of the styloid process.

  • Pulse Point: This artery is often used for pulse measurements; the styloid process being the most distal and lateral bony structure.

  • Additional Key Points:

    • Tendons are long and well defined while muscles lay over one another.

    • The pronator teres tendon does not reach the distal arm, and the pronator quadratus lacks a long tendon, with no muscles crossing over the artery.

    • Paired veins (venae comitantes) are present alongside the artery.

Ulnar Artery

  • Position: Found on the medial side of the distal forearm (pinky side), traveling with the ulnar nerve in a sheath surrounded by veins.

Radial Artery Details

  • Anatomical Guide: Lies lateral to the flexor carpi radialis tendon and medial to the brachioradialis tendon.

  • Linear Guide: From the center of the antecubital fossa to the base of the index finger.

  • Anatomical Limit: From 1 inch below the elbow bend to the base of the thumb (thenar eminence).

  • Origin: Originates at the bifurcation of the brachial artery.

  • Artery-Vein Relationship: Two small veins lie on either side (venae comitantes).

  • Incision: Made along the linear guide at the distal two-thirds of the forearm.

Ulnar Artery Details

  • Anatomical Guide: Lateral to the flexor carpi ulnaris tendon between it and flexor digitorum superficialis.

  • Linear Guide: From the center of the antecubital fossa to a point between the fourth and fifth fingers.

  • Anatomical Limit: From one inch below the elbow bend to the position over the pisiform bone (hypothenar eminence).

  • Origin: Bifurcation of the brachial artery.

  • Artery-Vein Relationship: As with the radial artery, two small veins are present on either side.

  • Incision: Along the linear guide, two-thirds up the distal forearm to expose the flexor carpi ulnaris muscle, and then pull it medially.

Arteries of the Body Trunk

  • Key Arteries: Right common carotid artery, costocervical trunk, vertebral artery, right subclavian artery, brachiocephalic trunk, etc.

  • The Aorta: Ascending Aorta: Originates from the left ventricle and branches as follows:

    • Left and Right coronary arteries (midsternal incision used for infants).

Arch of the Aorta

  • Branches Include: Brachiocephalic, left common carotid, left subclavian.

Right Subclavian

  • Extension and Branches: Extends from the right sternoclavicular articulation to the first rib with branches like vertebral, internal thoracic, and inferior thyroid.

Left Subclavian

  • Extension: From the level of the second costal cartilage to the first rib, with no branches.

Descending Thoracic Aorta

  • Branches: Contains nine pairs of thoracic intercostal arteries.

Descending Abdominal Aorta

  • Definition: Stretches from the diaphragm to the lower border of the fourth lumbar vertebra and branches into parietal (inferior phrenic, lumbar) and visceral (celiac axis, superior mesenteric).

  • Incision: Left of midline from the xiphoid process down to access.

External Iliac Artery

  • Description: A continuation of the common iliac artery that bifurcates into internal and external iliac arteries; located at the inguinal ligament, lateral to the external iliac vein.

  • Injection Usage: Applicable in both autopsied and obese unautopsied bodies, superficial.

Inguinal Region

  • Definition: Area below the inguinal ligament housing femoral vessels relying on bony landmarks.

  • Landmarks: Superior spine of the ilium and pubic tubercle as attachment points for the inguinal ligament.

External Iliac Details

  • Anatomical Guide: Lies anterior and medial relative to the peritoneum.

  • Linear Guide: An imaginary line extending upward from the linear guide of the femoral artery.

  • Anatomical Limit: Extends from the bifurcation of the celiac artery to underneath the inguinal ligament.

Femoral Triangle

  • Structure:

    • Base: inguinal ligament.

    • Walls: medial border of sartorius muscle and lateral border of adductor longus muscle.

    • Roof: fascia lata, which requires incision to expose.

  • Contents: The great saphenous vein lies over the femoral vein, which is located underneath the femoral artery. The great saphenous vein merges with it at the fascia lata's fossa ovalis.

  • Nodal Structures: Surrounded by inguinal lymph nodes possibly requiring resection.

Location of Femoral Vessels

  • Structures in Sheath: Three compartments:

    • Lateral: femoral artery

    • Medial: femoral vein

    • Medial: lymphatic vessels and nodes.

    • Best access is 1-2 inches from the base where they lie side by side.

  • Nerve Position: The femoral nerve is the most lateral structure at the triangle’s base.

  • Muscular Composition of Floor: Includes iliopsoas, pectineus, and adductor longus muscle, whose definitions may vary across sources.

Femoral Artery Details

  • Anatomical Guide: Passes through the femoral triangle, bounded laterally by sartorius muscle and medially by adductor longus muscle.

  • Linear Guide: From the center of the inguinal ligament to the center of the medial condyle of the femur.

  • Anatomical Limit: Extends from behind the center of the inguinal ligament to the adductor magnus muscle opening.

  • Origin: A continuation of the external iliac artery.

  • Artery-Vein Relationship: Lateral and superficial compared to the vein, with the vein being medial and deep.

  • Incision Location: Make an incision according to the linear guide, passing through the fascia lata.

  • Branches Include: Superficial epigastric, superficial circumflex iliac, external pudendal, profunda femoris.

Popliteal Fossa

  • Structure Formation: Formed by two muscle sets forming a trapezoid outlined in upper femoral and lower tibial triangles.

  • Boundaries: Lateral by biceps femoris heads and medial by semimembranosus and semitendinosus tendons.

  • Lower Tibial Triangle: Defined by gastrocnemius heads and plantaris muscle.

Contents and Access

  • Roof Structure: Composed of deep fascia and requires incision to visualize contents.

  • Major Contents: Tibial and peroneal nerves, popliteal vein, popliteal artery, and associated fat and lymphatic tissue.

  • Approaching Procedures: From the back of the knee, tibial nerve lies larger and more medial, while peroneal nerve is on the lateral aspect; popliteal vein is superficial to the artery.

  • Floor Structure: Formed by the lower end of the femur and knee joint capsule.

Popliteal Artery Details

  • Anatomical Guide: Located between the femur’s popliteal surface and the oblique popliteal ligament.

  • Linear Guide: Runs parallel from the superior border of the popliteal space to the inferior border.

  • Incision Approach: Standard practice allows some embalmers to perform the procedure from the side.

  • Anatomical Limit: From the adductor magnus opening to the lower border of the popliteus muscle.

  • Origin: A continuation of the femoral artery.

  • Artery-Vein Relationship: The vein lies posterior and medial to the artery, with the vein also described as superficial.

  • Branches: Includes five pairs of genicular arteries and five muscular branches.

Distal Leg

  • Key Arteries: The popliteal artery bifurcates into anterior and posterior tibial arteries, with the anterior tibial being superficial for convenient injection sites near the foot.

  • Anterior Tibial: Smaller terminal branch becoming the dorsalis pedis.

  • Posterior Tibial: Transforms into medial and lateral plantar arteries.

Anterior Tibial Details

  • Anatomical Guide: Positioned in the groove between the tibialis anterior muscle and the extensor hallucis longus tendon.

  • Linear Guide: From the lateral border of patella to the anterior ankle joint surface.

  • Anatomical Limit: Extends from the inferior border of the popliteus muscle to a point in front of the middle of the ankle joint.

  • Artery-Vein Relationship: The artery is superficial to the vein, which lies deep.

  • Incision Location for Foot Access: Near the ankle joint lateral to the tibia crest.

Posterior Tibial Details

  • Anatomical Guide: Between the posterior border of the tibia and the calcaneus tendon.

  • Linear Guide: From the center of the popliteal space to midway between the medial malleolus and the calcaneus.

  • Anatomical Limit: From the inferior border of the popliteus muscle to a position over the medial malleolus and calcaneus.

  • Artery-Vein Relationship: Artery is superficial while the vein is located deeper.

Tibial Branches

  • Details: Includes right and left peroneal branches and dorsalis pedis arteries.

Foot Anatomy

  • Artery and Nerves: The anterior tibial and deep peroneal nerve pass deep into the foot and allow easy visualization of arteries and veins due to loose skin and subcutaneous tissue.

Dorsalis Pedis Anatomy

  • Anatomical Guide: Not provided in referenced sources.

  • Linear Guide: From the center of the anterior surface of the ankle joint to a point between the first and second toes.

  • Anatomical Limit: Begins at ankle level, terminating at the toenail.

  • Incision Location: Midpoint between medial and lateral malleoli through the interosseous space.

Conclusion

  • References: Materials referenced include:

    • "Embalming: History, Theory, and Practice" by Gee-Mascarello – 6th Edition.

    • "Embalming: History, Theory, and Practice" by Mayer – 5th Edition. Graphics and charts utilized are credited as indicated throughout the material.