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1. Describe anatomical position, and define anatomical terms of spatial relationships, such as anterior/posterior, superior/inferior, medial/lateral, and proximal/distal, in relation to 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 position is described with a person standing, head, palms, & toes facing anteriorly (forward), and feet parallel.

There are numerous anatomical terms of spatial relationships that one must understand in communication with a healthcare team. Most of these are described in pairs describing the position of structures in comparison to one another. Most comparisons are made with consideration of anatomical position. These include:

• Superior (cranial) - nearer to head; Inferior (caudal) - nearer to feet

• Medial - towards the median plane; Lateral - away from median plane

• Anterior (ventral) - toward front surface; Posterior (dorsal) - toward back surface

Some relational anatomical terms are independent of anatomical position. These include:

• Proximal - towards trunk or point of origin; Distal - away from trunk of point of origin

Superficial - closer to surface; Deep - farther from the surface

2. Identify and differentiate between the four main types of anatomical planes (median, sagittal, frontal, and transverse).

Four imaginary planes intersect the body in anatomical position:

• Median plane: vertical plane passing longitudinally through the body (or structures) and divides the body into right and left sections

• Sagittal planes: vertical planes that run parallel to the median plane, dividing the body into right and left sections; may also be referred to as parasagittal or paramedian

• Frontal (coronal) planes: vertical planes that run perpendicular to the median plane, dividing the body into anterior and posterior sections

• Transverse (horizontal) planes: horizontal planes that run perpendicular to vertical planes, dividing the body into superior and inferior sections; may also be referred to as axial, cross-sectional or transaxial planes

Differentiation of these planes is important for accurate anatomical descriptions.

3. Differentiate between the layers of the integumentary system and deep fascia by categorizing each layer based on its location and anatomical characteristics, and apply this knowledge to common clinical situations.

The integumentary system is typically the first thing encountered in many healthcare situations, in addition to dissection. 

Due to visibility and accessibility, the skin is often the first thing considered in most physical exams (e.g. swelling, changes in color, damage to skin, etc.). Incision placement in skin is an important first consideration in surgeries.

During any early dissection, the first step is typically the removal of most superficial layers, starting with the skin.

The integumentary system is composed of skin plus the superficial fascia layer is also considered a component.

The skin has two main layers:

Epidermis: most superficial (visible) epithelial layer

• Composed mainly of dead, keratinized, flattened cells; avascular; protective layer

Dermis: deep to epidermis; connective tissue layer

• Highly vascular; supplies blood to deeper epidermal layers

• Contains afferent nerve endings (some penetrate to deep epidermis) for sensations such as pain, temperature, pressure, etc.

• Contains sudoriferous (sweat) glands, sebaceous (oil) glands, hair follicles and associated arrector pili mm.

Deep to the skin are the different types of fascia. Fascia is the term for grossly visible connective tissue collections or sheaths deep to the skin.

Superficial fascia (i.e. hypodermis, subcutaneous tissue): just deep to dermis

• Often called the fatty layer due to its high content of loose areolar connective tissue

  • Thickness varies among individuals and body regions

• Many of the structures located in dermis are also located here

Deep fascia

• Dense connective tissue; Is located deep to superficial fascia but also extends into deeper regions

• Surrounds and supports muscles, organs and neurovascular structures

Clinical correlation: Skin laceration repair (sutures) is an important consideration with the integumentary system, typically involving all layers of the integumentary system (epidermis, dermis, and superficial fascia). Alignment and repair is mainly afforded by the dermal layer both in terms of strength but also importantly the typical alignment of collagen fibers, which have a predictable pattern in the dermis (tension lines).

4. Define muscle attachment point terminology (origin, insertion, proximal/distal attachments) and describe their impact on joint movement.

When describing skeletal muscle anatomy, knowledge of attachment points is essential as this helps identify the joint(s) the muscle crosses. Understanding these points provide insight into the types of actions that can occur when a muscle shortens through concentric contractions. Typically when a muscle shortens, one of its attachment points is ‘fixed’ (stable) while the other attachment point is more mobile, pulling toward the fixed point.

Traditional terminology related to muscle attachments includes:

• Origin:

  • Typically, the proximal or superior end of the muscle

  • Usually considered the fixed point that does not move during contraction

• Insertion

  • Typically, the distal or inferior end of the muscle

  • Usually considered the kinetic point (moves toward the origin during muscle contraction)

It is important to note that although the origin of a muscle is typically considered fixed, exceptions exist. Consequently, there is a shift towards more descriptive terms such as proximal and distal attachments. While traditional terms like origin and insertion still appear in other resources, we will use the more descriptive terms to promote clarity and accuracy.

Bones have numerous attachment sites, known as bone markings, that serve as attachment points for tendons (connecting muscle to bone), ligaments (connective bone to bone), and fascia. The size and shape of these attachment sites can change throughout life based on activity level and mechanical stresses at these points.

Understanding muscle attachments on bone may seem daunting, we will highlight those that are most clinically relevant. Understanding these are important for a variety of clinical reasons, including orthopedic assessment, surgical implications, understanding developmental and age-related changes, and rehabilitation and strength training.

5. Describe the components and functions of neurovascular bundles, and explain how compression injuries like compartment syndrome can affect them.

To properly function, all visceral structures, including muscle and skin, rely on the following components:

• Blood supply (for oxygen & nutrients) via arteries

• Drainage of low-oxygen blood to the heart via veins

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

• Innervation (communication with the CNS) via nerves

These structures often travel together as neurovascular bundles, which are usually enveloped in deep investing fascia. When considering muscle, the neurovascular bundles are typically located deep to the muscle.

Since these structures travel together and are wrapped in fascia, they also may be affected together if there is injury or compression in that area. One example (with more detail later in the curriculum) is compartment syndrome, where increased pressure in muscle compartments can compromise blood supply, venous & lymphatic drainage, and innervation to the affected area. If untreated, compartment syndrome can lead to pain, tissue ischemia and necrosis.

6. Describe the anatomy and structure of the vertebral column, including the five regions and major joints.

The vertebral column is a complex structure comprising 33 vertebrae and associated joints that extend from the occipital bone of the skull to the coccyx. It is divided into 5 regions, each containing distinct types of vertebrae.

Cervical spine - neck region; 7 vertebrae

• Smallest of movable vertebrae and allows for significant movement

• Trauma or degenerative disorders of these vertebrae can affect cervical spinal nerves that exit here and depending on severity can cause pain, numbness, and/or weakness in upper limbs. If severe, it could affect the spinal cord which traverses these vertebrae, and this could affect most structures distal/inferior to this area.

• Thoracic spine - thorax/ribs region; 12 vertebrae

• Articulates with ribs and because of this association is the least mobile of the movable vertebrae

Lumbar spine - lower back region; 5 vertebrae

• Largest vertebra; Bears a significant portion of body weight and allows for flexibility and mobility of lower back

• Lumbar spine issues, such as herniated discs or lumbar stenosis, are common sources of lower back pain and can affect lumbar spinal nerves causing symptoms in the lower limb

Sacrum - pelvic region; 5 fused vertebrae (immovable)

• Articulates with the hip (coxal) bones at sacro-iliac (SI) joints

Coccyx - lower pelvic region; 4 fused vertebrae (immovable)

All movable vertebrae have two types of joints:

• Intervertebral (IV) disc: a midline cartilaginous joint between the bodies of adjacent vertebrae

  • The inferior-most IV disc sits between the body of L5 and articular surface of the sacrum

  • Herniated discs (‘slipped discs’) occur when the inner layer (nucleus pulposus) herniates through the outer layer (anulus fibrosus) of the IV disc; the herniated portion can impinge on spinal cord or spinal nerves

Facet joints: 2 pairs per vertebrae

7. Analyze the structural and functional components of the anterolateral and anterior abdominal walls, and explain their significance in minimizing neurovascular injury during surgical procedures.

To minimize the risk of neurovascular injury and ensure optimal closure while minimizing scarring and potential damage to deep structures, a comprehensive understanding of abdominal wall anatomy is essential. The abdominal wall consists of two major regions that are interconnected: the anterolateral & anterior abdominal walls.

Anterolateral Abdominal Wall

There are 3 anterolateral abdominal wall muscles that are often referred to colloquially as ‘the obliques’: from superficial to deep, external oblique, internal oblique, and transversus abdominis mm.

Muscle fibers are oriented at different angles to provide structural support, maintain abdominal tone, and enable lateral trunk flexion. The aponeuroses (or tendinous expansions) of these muscles extend anteriorly to form the rectus sheath.

Anterior Abdominal Wall

This wall shares a similar structural organization with the anterolateral wall but has a few distinct features.

The rectus sheath is composed of the aponeuroses of the three anterolateral abdominal muscles and encloses the rectus abdominis mm. It has an anterior and posterior layer, with the posterior layer being incomplete in the inferior abdomen. The linea alba is the midline portion of the rectus sheath that runs from the xiphoid process of the sternum to the pubic symphysis. This serves as the medial-most anchor for muscle attachments from both sides and comparatively lacks neurovasculature.

The rectus abdominis mm. are the straight/vertical muscles that span from the inferior rib cage to the pubic bone within the rectus sheath. These muscles facilitate trunk flexion and compresses abdominal viscera. Tendinous intersections are dispersed throughout the muscle and attach to the anterior rectus sheath. When these muscles are tensed or hypertrophied, the muscle bulges around the intersections creating a ‘six-pack’ appearance, particularly in individuals with relatively little adipose tissue in the superficial fascial layer.

Neurovascular Supply of Abdominal Wall

Innervation

The abdominal wall receives regular, segmental innervation (no plexus formation) through the ventral primary rami (VPRs) of spinal nerves thoracic spinal nerves T7-T12. The 1st lumbar spinal nerve (L1) innervates the most inferior portions of the abdominal wall.

Vasculature

The primary arteries in this area are the superior and inferior epigastric aa., with the inferior epigastric a. serving a great area in this region. These arteries have different source arteries: superior epigastric (from the internal thoracic a.) and the inferior epigastric a. (from the external iliac a.). These arteries naturally anastomose (connect). Arterial anastomoses are important in allowing blood flow to continue in cases where a pathway is obstructed - obstructions could be caused by pathology, joint movements, or surgical interventions.