CLC Practical 1.1 - Introduction to Anatomy - Comprehensive Notes

CLC Practical 1.1 - Introduction to Anatomy

Introduction

• The class covers the following learning outcomes:
  • Rules and regulations of HARC (Human Anatomy Resource Centre)
  • Introduction to the cadaver
  • Introduction to prosected material

Introduction to the Cadaver

• The class will be introduced to a cadaver for the first time, with a gradual, step-wise approach.
• Staff will take a careful and measured approach, acknowledging that it can be an emotive experience for many.
• Cadavers may not look as expected; colour, appearance, and texture of skin is altered during embalming.
• The process of body donation will be explained, and time will be allocated for questions.
• If anyone feels uncomfortable, they should inform a staff member.
• Respect HTA regulations and maintain professionalism/respect towards tissue at all times.
• The cadaver should be treated as the first patient, with the same respect as living patients in hospitals.
• Most classes involve human tissue in some form, called prosections, which are prepared to show specific structures of interest.
• The process begins by only removing the sheet covering the body.
• The process of body donation, unique ID numbers etc. will be discussed.
• The embalming procedure includes washing/shaving, injection, and tagging.
• When examining prosections involving the face, the face remains covered unless examining structures in the practical, out of respect to the donor.

Practical Stations

• Most practicals are divided into 4 stations (A - D), and students rotate around every 20 minutes.
• Each station has a booklet to work through using the prosections and models available.
• Booklets are in plastic covers that are wiped down after each practical and designed to be handled while wearing gloves.
• If struggling or having questions, raise a hand for a demonstrator to assist.

Station A: Anatomical Position, Terminology, and Planes

• Learning outcomes:
  • Anatomical position and planes
  • Surface anatomy and vertebral levels

A1 - Anatomical Position and Planes

• The anatomical position is the standard reference position for the human body in anatomy.
• In the anatomical position:
  • Soles of the feet are firmly planted and parallel.
  • Palms are facing forwards (anterior) with the thumbs away from the midline of the body (laterally).
• When describing a structure anatomically, always use the anatomical position to avoid confusion.
• The body can be divided using three anatomical planes:
  • Coronal
  • Sagittal
  • Transverse
• Understanding these planes is important for interpreting the relationship of organs and understanding medical images (CT and MRI scans).

Anatomical Terminology

• Using anatomical terminology is vital in clinical medicine for communicating information about the body and its structures.
• Remember to describe anatomical terminology in the anatomical position, unless otherwise stated.
• Example:
  • In the anatomical position, the thumb is lateral to the other four digits.
  • If the forearm is pronated (palms facing posteriorly/backwards), the thumb becomes the most medial digit.
• Anatomical Terms:
  • Anterior and Posterior
  • Ventral and Dorsal
  • Medial and Lateral
  • Superior and Inferior
  • Proximal and Distal
  • Cranial and Caudal
  • Superficial and Deep

A2 - Surface Anatomy and Vertebral Levels

• The surface anatomy (surface projection) of internal organs is key to clinical examination.
• Vertebral levels and major landmarks are used to describe the main organs of the body.
• A vertebral level is an imaginary line drawn in a transverse plane across the body.
• Key vertebral levels in the thorax and abdomen:
  • Suprasternal (jugular) notch is at vertebral level T2.
  • Sternal angle is at vertebral level T4.
  • Xiphoid process is at vertebral level T9.

Abdominal Quadrants

• The abdomen can be divided into quadrants to visualize the surface anatomy of various organs.
• Quadrants are formed by:
  • A vertical line from the suprasternal (jugular) notch to the pubis (sagittal plane).
  • A horizontal line through the umbilicus (belly button) called the transumbilical plane.
• The four quadrants are:
  • Left upper quadrant
  • Left lower quadrant
  • Right upper quadrant
  • Right lower quadrant

Station B: Skeleton and Vertebral Column

• Learning outcomes:
  • Major features of axial and appendicular skeleton
  • Anatomical terminology - humerus

B1 – Axial and Appendicular Skeleton

• Bones of the skeleton can be categorized into axial and appendicular skeletons.
• The axial skeleton includes bones of the core (central axis) of the body, such as:
  • Skull
  • Hyoid bone
  • Vertebrae
  • Sternum
  • Rib cage
• The appendicular skeleton is composed of bones attached to the axial skeleton, forming the upper and lower limbs:
  • Joined to the axial skeleton via osteological “girdles”.
  • The upper limb is joined via the pectoral girdle (scapula and clavicle).
  • The lower limb is joined via the pelvic girdle (hip bone).

B2 – Anatomical Terminology (Humerus)

• Bones are a dense connective tissue composed of organic and non-organic components.
• The non-organic part is mineralized tissue made of calcium and phosphate called hydroxyapatite.
• In most bones, this mineralized tissue is divided into either compact bone or trabecular bone.
• Bones are highly vascular and supplied by nutrient arteries that supply the bone marrow, trabecular bone, and inner layers of compact bone.
• Bones are covered externally by a connective tissue called the periosteum, with a rich nerve and blood supply, critical in healing bone fractures.
• The humerus is a main bone of the upper limb, part of the appendicular skeleton, connecting with the axial skeleton via the pectoral girdle (scapula and clavicle).
• Features of the Humerus:
  • Anterior
  • Posterior
  • Medial
  • Lateral
  • trabecular bone
  • compact bone
  • epiphysis (proximal and distal)
  • diaphysis (shaft)
  • head
  • anatomical neck and surgical neck
  • greater tubercle
  • lesser tubercle
  • intertubercular groove
  • olecranon fossa
  • lateral epicondyle
  • medial epicondyle
  • trochlea

Station C: Vertebrae and the Rib Cage

• Learning outcomes:
  • Major features of regional vertebrae
  • Major features of sternum and typical rib

C1 – Types of Vertebrae

• The vertebral column is composed of 33 individual vertebrae divided into cervical, thoracic, lumbar, sacral, and coccygeal regions.
• Vertebrae can be divided into typical and atypical vertebrae.
• Typical vertebrae share common features within each region:
  • Vertebral body
  • Spinous process
  • Transverse process
  • Lamina
  • Pedicle
  • Vertebral foramen (for spinal cord)
  • Intervertebral foramen (for spinal nerve)
• Unique Features by Region:
  • Cervical:
    • Are the most varied.
    • Have a hole in the transverse process called foramen transversarium.
    • Have a bifid (split in two) spinous process (except for C7).
    • C1 (atlas) and C2 (axis) are given specialized names and have specialized features designed for the mobility and stability of the skull.
  • Thoracic:
    • Facets on the vertebral body and transverse process for the ribs.
    • Very long and downward-facing spinous process.
  • Lumbar:
    • Very large vertebral bodies, sometimes kidney-shaped.
    • Short, stumpy spinous processes.
    • No facets on the vertebral body or transverse processes.
  • Sacral and coccygeal:
    • 5 sacral vertebrae are fused together.
    • Variable number of small coccygeal vertebrae between people (human variation).

C2 – Sternum and Ribs

• The sternum is a flat, long bone on the anterior surface of the thorax.
• Together with the ribs, costal cartilages, and thoracic vertebrae, it forms the rib cage, protecting the heart, lungs, and major vessels.
• It articulates with the clavicle, joining the upper limb to the thorax via the pectoral girdle.
• The sternum is composed of 3 main parts:
  • Manubrium
  • Body of the sternum
  • Xiphoid process
• Features of the Sternum:
  • Suprasternal (jugular) notch
  • Clavicular notch (articulation of the clavicle)
  • Sternal angle
  • Facets for the attachment of costal cartilages of the ribs
  • Xiphoid process
• Ribs are long flat bones.
• There are 12 pairs of ribs (left and right) for a total of 24 ribs.
• Ribs are classified into “true ribs” and “false ribs”.
• True ribs are the first 7 pairs of ribs and are physically attached to the sternum via the costal cartilages.
• False ribs are the lower 5 pairs.
• Rib pairs 8-10 have a common costal attachment.
• Rib pairs 11 and 12 are known as “floating ribs” because they have no anterior attachment to the sternum and are only attached posteriorly to the thoracic vertebrae.
• Features of a Rib:
  • Head of the rib with its 2 articulating facets (superior facet and inferior facet)
  • Neck
  • Tubercle with articulating facet
  • Angle of the rib
  • Costal groove (inferior surface)
  • External and internal surfaces
  • Medial end where costal cartilage articulates
• Articulation of Ribs and Vertebrae:
  • The superior facet on the head of the rib connects to the vertebral body above it.
  • The inferior facet on the head of the rib will connect to the vertebral body of the same number, e.g., rib 7 connects with thoracic vertebra 7.
  • The facet on the tubercle of the rib will articulate with the transverse process of the thoracic vertebra of the same number.

Station D: Introduction to Medical Imaging

• Learning outcomes:
  • Introduction to medical imaging – chest radiograph
  • Vertebral column and intervertebral discs
  • Rib cage and intercostal muscles

D1 - Introduction to Medical Imaging

• Medical imaging is an essential diagnostic tool.
• It is paramount to appreciate “normal” anatomy before diagnosing “abnormal”.
• Different types of imaging modalities include:
  • X-ray plain radiographs – chest, abdominal etc.
  • Contrast medium radiographs – angiograms, barium studies, pyelograms etc.
  • Histological microanatomy images
  • Computed tomography (CT) scans
  • Magnetic resonance imaging (MRI) scans
  • Nuclear medicine imaging
  • Positron emission tomography (PET)
• X-ray Plain Radiographs:
  • Provide good detail of bones and other dense structures.
  • Chest X-rays are viewed as if the patient is facing you in the anatomical position.
  • The left side of the body is seen on the right of the image and vice versa.
  • Different tissues absorb different amounts of the X-ray beam, resulting in different colors.
  • Air and water show up as black.
  • Soft tissue as different shades of grey.
  • Bone as white.

D2 – Vertebral Column and Intervertebral Discs

• The vertebral column is the central osteological axis of the human body.
• The adult human vertebral column has 4 distinct curvatures – 2 primary curvatures and 2 secondary curvatures.
• Curvatures allow for equal distribution of the centre of gravity and helps with flexibility and movement of the trunk.
• Primary Curvature:
  • Anterior concave curve that appears during the early stages of the embryo.
  • Retained throughout life in the thoracic and sacral regions.
  • Also known as kyphoses (plural) – the thoracic kyphosis and the sacral kyphosis.
• Secondary Curvature:
  • Anterior convex curves in the cervical and lumbar regions.
  • Appear as a human learns to hold up their head as babies and to stand and walk as toddlers.
  • Also known as lordoses (plural) – the cervical lordosis and the lumbar lordosis.
• Intervertebral Discs:
• There are 23 IV discs in total: 6 cervical, 12 thoracic and 5 lumbar.
• The IV disc forms a fibrocartilaginous joint between the vertebral bodies above and below it which allows slight movement of the vertebrae.
• It also acts as a shock absorber and helps to hold the vertebrae together.
• Intervertebral discs consist of an outer fibrous ring, the anulus fibrosus, which surrounds a softer, gel-like centre, the nucleus pulposus.
• This allows the disc to withstand compressive forces and to distribute pressure evenly across the disc.

D3 – Rib Cage and Intercostal Muscles

• The rib cage consists of the sternum, costal cartilages, 12 thoracic vertebrae, 24 ribs, and intercostal muscles.
• It protects the heart, lungs, and other thoracic structures while retaining mobility to aid in breathing.
• Features of the Rib Cage:
  • Costal margin
  • Suprasternal (jugular) notch
  • Costal cartilage
  • True rib and a false rib
  • Intercostal space
  • Transverse process of a thoracic vertebra
• Intercostal Spaces and Intercostal Muscles:
  • The spaces between the ribs are known as intercostal spaces and are filled with intercostal muscles and a neurovascular bundle.
  • There are 3 intercostal muscle layers that overlap each other, and each layer has muscle fibres passing in different directions.
    • External intercostal: muscle fibres pass down and in (inferiorly and medially)
    • Internal intercostal: muscle fibres pass down and out (inferiorly and laterally)
    • Innermost intercostal: muscle fibres are almost vertical or the same as the internal intercostal
  • A neurovascular bundle is a structure that contains a vein, artery, and a nerve (VAN) bundled together.
  • The intercostal neurovascular bundle runs along the inferior border of each rib in the costal groove, sandwiched between the internal and innermost layers of the intercostal muscles.