2. Describe ‘anatomical position.’ Define anatomical terms of spatial relationships (based on anatomical position). 

To best communicate and understand relationships of body parts and structures, one must understand anatomical position. All anatomical, relational terminology is based on the visualization of the patient or donor in anatomical position, even when they are supine (lying on back), prone (lying face-down), or on their side. 

Anatomical Relational Terminology

3. Describe anatomical planes used to describe the human body. 

There are four types of imaginary planes that intersect the body in the anatomical position: median, sagittal, frontal, & transverse.

Median plane: vertical plane passing longitudinally through the body (or structure) midline, divides right and left halves.

Sagittal planes: vertical planes passing through the body parallel to the median plane, divides right and left portions.

Frontal (coronal) planes: vertical planes passing through the body at right angles to the median plane, divides anterior and posterior portions.

Transverse (horizontal) planes: planes passing through the body perpendicular to any of the vertical planes, divides superior and inferior portions.

4. What are attachment sites for muscles? Understand the terms origin, insertion, and proximal/superior & distal/inferior attachments.

Bones may have numerous attachment sites (bone markings) that are attachment points for tendons (connecting muscle to bone), ligaments (connecting bone to bone), and fascia. The size and shape of attachments sites will change throughout life based on the activity (or lack thereof) at these points.

When describing the anatomy of a muscle, attachment points are commonly included. Knowing these attachment points gives the learner an understanding of what joint(s) the muscle crosses (and thus can directly affect) and a basic understanding of what types of actions can occur due to a muscle when concentrically contracting (muscle shortening).

Traditional terminology relating to muscle attachments

Origin

• Typically proximal or superior end of muscle

• Typically fixed (does not move during contraction)

Insertion

• Typically distal or inferior end of muscle

• Typically kinetic (will often move towards the origin of the muscle)

It is important to note that although the proximal or superior end of a muscle is typically fixed, this is not always the case. There has been a movement towards the usage of the more descriptive and accurate terms: proximal or superior attachments and distal or inferior attachments. You still may see the terms origin and insertion in other resources, but we will not use that terminology.

5. Describe the difference between afferent and efferent innervation.

Most of the nerves have both afferent and efferent fibers packaged together. In fact if not explicitly stated as a purely afferent or efferent nerve, assume that any named nerve has both types of fibers.

When thinking of afferent (sensory) innervation, think carrying information away from an organ or sensory receptor or information arriving at the central nervous system (CNS).

Types of afferent (sensory) fibers:

• Somatic afferent

  • Most commonly discussed afferent fiber

  • Sensation from skin

    • Pain, touch, pressure, and temperature

    • Dermatome maps depict the different conceptual areas of skin afferently innervated by a single cranial or spinal nerve.

  • Proprioception

    • Conveys information to CNS regarding positioning of a joint or the degree of tension in muscle tendons

    • When discussing afferent innervation of a muscle, this is what one is describing

• Visceral afferent

  • Conveys information from hollow viscera (organs) and blood vessels

    • Pain or reflex sensations, such as pressure (e.g. blood) or organ distension

• Special afferent (typically described as special sensory)

  • Associated with special senses (vision, olfaction, hearing, taste, & equilibrium)

  • Fibers of certain cranial nerves

With efferent (motor) innervation, think of carrying information from the CNS to an effector organ, to create an effect (such as muscle contraction or glandular secretion).

Types of efferent (motor) fibers:

• Somatic efferent

  • Impulses from the CNS to skeletal muscle (can lead to contraction)

  • When discussing what nerve innervates a muscle, often considering this aspect of innervation

    • However, most named, somatic nerves have both efferent and afferent fibers, particularly those derived from plexuses.

• Visceral efferent

  • Impulses from the CNS to glands and smooth muscle

  • Associated with autonomic nervous system

6. Describe the typical contents of a neurovascular bundle.

All visceral structures, including muscle and skin, require four things to function properly:

• Blood supply via arteries

• Drainage of low-oxygen blood to heart via veins

• Drainage of fluids, proteins, and cellular debris via lymphatics

• Innervation (communication with the CNS) via nerves 

These structures often travel together in a neurovascular bundle. These bundles are often wrapped or enveloped in deep investing fascia. When considering muscle, the neurovascular bundle typically are located deep to the muscle.

7. Identify and detail the muscles of the anterior thorax: pectoralis major m., pectoralis minor m., and serratus anterior m. 

Pectoralis major m.

• Proximal attachments:

  • 2 heads:

    • Clavicular (clavicle)

    • Sternocostal (sternum and costal cartilages)

• Distal attachment:

  • Shared tendon on proximal humerus

  • Crosses the glenohumeral (shoulder) joint

• Action(s):

  • Both heads contracting simultaneously:

    • Adduction & medial rotation of glenohumeral joint

  • Clavicular head independently:

    • Flexion of glenohumeral joint

  • Sternocostal head contracting independently

    • Extension of glenohumeral joint (from flexed position)

Action videos

• Innervation:

  • Two nerves derived from the brachial plexus

    • Lateral pectoral n.

    • Medial pectoral n.

• Dominant arterial supply:

  • Thoraco-acromial a. (branch of axillary a.) branches

• Clinical considerations:

  • Breast pathology & surgery

    • Due to the close anatomical relationship, pectoral fascia and muscle can be affected or resected.

Pectoralis minor m.

• Proximal attachments: anterior ribs 3-5

• Distal attachment: coracoid process of scapula

• Actions

  • Stabilization of scapula to allow for efficient movements at other joints, specifically the glenohumeral joint

  • Protraction (moving the scapula anteriorly)

• Innervation: medial pectoral n.

• Dominant arterial supply: thoraco-acromial a. (branch of axillary a.) branches

• Anatomical relationships:

  • Medial pectoral n. pierces the pectoralis minor m.

  • Important anatomical landmark locating branches of the axillary a. both in the lab, in imaging, and in surgeries

    • Subdivides the artery into 3 parts based on relationship to the muscle (medial, deep, or lateral to)

Serratus anterior m.

• Proximal attachments: Ribs 1-8

• Distal attachment: anterior surface of scapula

• Actions:

  • Protraction of scapula

  • Upward rotation of glenoid fossa

    • Important for allowing full range of motion for the glenohumeral (shoulder) joint, particularly in abduction and flexion

  • Stabilization of scapula

• Innervation: long thoracic n.

  • The placement of this nerve is unique in that it is superficial to the muscle

• Clinical considerations:

  • With injury to the long thoracic n., the scapula may develop a wing-like appearance (‘winged scapula’)

    • The medial border of the scapula is displaced posteriorly in comparison to the uninjured side. This is particularly evident when the shoulder joint is flexed (as in pushing against a wall with the upper limb).

    • This affects scapular motion, but (more importantly) prevents full range of motion at the glenohumeral joint

8. Identify and detail the muscles of the anterior neck: sternocleidomastoid m., infrahyoid mm.

• • Sternocleidomastoid m.

• Superior attachments:

  • Mastoid process of temporal bone & occipital bone

• Inferior attachments:

  • Manubrium of sternum

  • Medial clavicle

• Actions:

  • Bilateral contractions: flexes cervical vertebrae

  • Unilateral contraction: lateral flexes the neck & rotates the head in the opposite direction

• Innervation:

  • Efferent: Accessory n. (CN XI)

  • Afferent: C2 & C3 fibers

  • It is uncommon that separate nerves provide afferent and efferent innervation to a muscle.

• Anatomical relationships:

  • Prominently visible and palpable landmark in the neck

  • External jugular v. typically runs anterior/superficial to this muscle

Infrahyoid mm.

The infrahyoid muscles are a set of 4 muscles (sternohyoid, omohyoid, sternothyroid, and thyrohyoid mm.) located inferior to the hyoid bone. This set of muscles is often referred to as strap muscles due to their ribbon/strap-like shape. 

• The names of the muscles indicate the attachment points:

  • Omo-: means shoulder (in this case, attached on the scapula)

  • Thyro(id): indicates the thyroid cartilage, not thyroid gland

• Actions

  • Stabilization or depression of hyoid

  • Dependent on muscles, will pull larynx either superiorly, or inferiorly

• Innervation

  • Ansa cervicalis (cervical plexus) for 3 of the 4 muscles

• Anatomical relationships:

  • Arranged in two layers

    • Superficial: sternohyoid & omohyoid

    • Deep: sternothyroid & thyrohyoid

  • To access the thyroid gland, these muscles have to be reflected or moved

9. Describe the location of the thyroid and parathyroid glands. Understand details regarding function and vascular supply and drainage of these glands.

The thyroid gland has two lobes connected by a central isthmus, and sits between the C5-T1 vertebra. Nearly 50% of people have an accessory (pyramidal) lobe, which varies in size and typically connects the isthmus of the thyroid gland to the hyoid bone (Moore et al., 7th edition).

The thyroid gland is an endocrine gland - meaning it secretes hormones and is ductless. The thyroid gland secretes thyroid hormones (controls rates of tissue metabolism) and calcitonin (important in calcium homeostasis).

Arterial supply of the thyroid gland

• Superior thyroid a.

  • Typically the first branch of the external carotid a. 

• Inferior thyroid a.

  • Branch of thyrocervical trunk of the 1st part of the subclavian a.

  • Typically crosses the recurrent laryngeal n. deep to the thyroid gland in the vicinity of the larynx

    • Clinical consideration: when ligating this artery during a thyroidectomy, care must be taken to not damage the recurrent laryngeal n., which innervates most intrinsic laryngeal muscles and inferior larynx.

Venous drainage of the thyroid gland

• Superior thyroid v.

• Middle thyroid v.

• Inferior thyroid v.

Parathyroid glands may be found in a variety of locations, but are typically on the posterior aspect of the thyroid gland. There are typically four parathyroid glands (a superior pair and inferior pair), but there may be more or fewer. The superior parathyroids are the most constant in size and position. Parathyroid glands may be supplied by either set of thyroid arteries (as determined by location), but typically the inferior thyroid aa. supply the parathyroids. The parathyroid glands are also endocrine, and produce parathyroid hormone (PTH). 

10. Locate and explain the relevant anatomical relationships and clinical significance of the linked anatomical structures.

Review an atlas (like BlueLink and/or other illustrations) of the list of structures as pre-work. Majority of exploration for this learning objective will occur during laboratory scheduled time.