Chapter 1: Introduction & the Language of Anatomy

Anatomy is the study of the structure of living organisms. For a future doctor it means one thing in particular: the structure and composition of the human body, and how that structure explains function, examination findings and disease. Almost every clinical conversation ("pain radiating down the medial arm", "a fracture of the distal radius", "a lesion in the left internal capsule") is spoken in anatomical language, so the first job is to learn that language well.

Anatomy is taught in two standard vocabularies side by side: English and Latin (the international Terminologia Anatomica). Practicum identification uses the Latin names, so this ebook gives both.

How anatomy is taught here

The anatomy and embryology curriculum is systemic: each block covers one body system, and anatomy is studied alongside that block's physiology, histology and biochemistry.

A practicum topic runs as a fixed sequence: asistensi (the teaching session these notes are built from) → pretest → practicum → report → responsi (the practical exam), with inhal/refrat or remedial work for anyone who falls short.

How to study it

1. Start with the big picture. Look at the whole region or bone before any detail: which side is it, which way is up, what is it connected to?
2. Zoom in step by step, from the bone to its surfaces, then to the features on each surface.
3. Don't rush. Anatomy is cumulative; a vague foundation makes every later block harder.
4. Keep it simple. Group structures by pattern (for example, "every muscle of the anterior arm is a flexor supplied by one nerve") instead of memorising lists.
5. Teach someone else. Explaining a structure aloud is the fastest way to find the gaps.

A few anatomical facts to anchor the scale. The femur is the longest, heaviest and strongest bone in the body; the stapes, in the middle ear, is the smallest. An adult's blood vessels laid end to end are often estimated at roughly 100,000 km, and the intestine from duodenum to rectum measures about 6–8 m.

The anatomical position

Every description in anatomy assumes the body is in the anatomical position:

• standing upright, head and eyes facing forward;
• upper limbs hanging at the sides with the palms facing forward;
• lower limbs together, feet flat and toes pointing forward.

This matters because it fixes "anterior", "lateral" and the rest, regardless of how a patient is actually lying. A patient lying on their back is still described as if standing in the anatomical position: the thumb is always lateral, and the palm is always anterior (palmar).

Regions of the body

The body surface is divided into named regions (regiones). They are used to describe where a structure sits or where a patient reports symptoms. Some you will use constantly:

Anatomical planes and sections

An anatomical plane is an imaginary flat surface that divides the body. Planes let us describe where a structure lies, which way a movement goes, and which orientation a scan or a cut specimen shows.

• Median (midsagittal) plane: the single vertical plane through the midline, dividing the body into right and left halves.
• Sagittal (parasagittal) planes: any vertical plane parallel to the median plane, off the midline.
• Frontal (coronal) planes: vertical planes at right angles to the median plane, dividing the body into anterior (front) and posterior (back) parts.
• Transverse (axial, horizontal) planes: at right angles to both, dividing the body into superior (upper) and inferior (lower) parts.

Sections (sectio)

A section is a cut made along a plane. It is the language of specimens, CT and MRI:

• Sectio longitudinalis: a cut along the long axis of the body or a part. It can lie in a median, sagittal or coronal plane.
• Sectio transversalis: a cut at right angles to the long axis, giving the familiar round cross-section of a limb or the axial slice of a CT.
• Oblique section: any cut at an angle between the two.

Clinical relevance. A fracture seen on an anteroposterior radiograph is viewed in the coronal plane, so the same limb is always also imaged from the side (lateral view) before displacement can be judged. Brain imaging is routinely reconstructed in all three planes (axial, coronal and sagittal), because a lesion that looks small in one plane may be large in another.

Directional terms

Directional terms describe the position of one structure relative to another, always from the anatomical position.

Two pairs cause most mistakes:

• Proximal/distal is not the same as superior/inferior. Proximal means closer to the origin, not "higher". In the limbs the origin is the trunk, so the elbow is proximal to the wrist. In a tube it is the start of the tube: the caecum is the proximal colon and the sigmoid colon is distal, even though the sigmoid is not lower in every direction.
• Anterior/posterior versus ventral/dorsal in the brain. Because the neural axis bends at the midbrain, "dorsal" in the forebrain points upward, not backward. Different regions use slightly different conventions, so learn the terms as they are used for each region.

On the hand and foot, palmar (volar) is the palm side and plantar the sole; dorsum is the back of the hand or the top of the foot.

Topographic terms

A few more words describe position within a structure:

• Supra- (above) and infra-/sub- (below): fossa supraspinata lies above the spine of the scapula, fossa infraspinata below it.
• Apex (tip) and basis (base) describe cone- or pyramid-shaped structures. The apex of the lung points up, while the apex of the heart and of the sacrum point down, so apex does not mean "top".
• Internus/externus, centralis/peripheralis and superficialis/profundus work the same way everywhere.

Lateralization

• Unilateral: on one side only.
• Bilateral: on both sides.
• Ipsilateral: on the same side as a reference point.
• Contralateral: on the opposite side.

Clinical relevance. A bilateral, symmetrical rash on both legs points toward a systemic cause (for example a vasculitis). A stroke in the left cerebral hemisphere causes weakness of the contralateral (right) side of the body, because the motor pathways cross.

Imaginary lines on the trunk

Vertical reference lines are used to locate structures on the chest and back, for example to place a stethoscope or a chest drain.

The axillary lines are defined with the arm raised: the anterior axillary line follows the anterior axillary fold (pectoralis major), the posterior line follows the posterior fold (latissimus dorsi), and the midaxillary line runs halfway between them.

Anatomical nouns: reading a Latin name

Most anatomical names are built from a small vocabulary. Once you know it, a new name usually explains itself.

Start every answer with the type of structure

Every anatomical name begins with what kind of structure it is: os tibia, m. biceps brachii, a. subclavia, n. vagus. In a practicum answer the prefix is part of the name. "Biceps brachii" alone is incomplete; "m. biceps brachii" is correct.

Movements

Movements happen at joints, in a plane, around an axis at right angles to that plane.

For the thumb and the fingers the reference is the hand, not the body: fingers abduct away from the middle finger, and the thumb flexes across the palm.

Osteology: bones

Osteology is the study of bones. Bones are classified by shape:

• Long bones, longer than they are wide, such as the humerus and femur.
• Short bones, roughly cube-shaped, such as the carpal bones.
• Flat bones, thin plates, such as the parietal bone and sternum.
• Irregular bones, with complex shapes, such as the vertebrae.
• Sesamoid bones, which develop inside a tendon, such as the patella.

Parts of a long bone

• Epiphysis: each expanded end. It is filled with spongy bone (red marrow) and covered by articular (hyaline) cartilage where it forms a joint.
• Metaphysis: the flared zone between epiphysis and shaft. In a growing bone it contains the epiphyseal (growth) plate; in adults only an epiphyseal line remains.
• Diaphysis: the shaft, a tube of compact bone around the medullary cavity (yellow, fatty marrow in adults).
• Periosteum: the fibrous membrane covering the outer surface. It carries nerves and blood vessels into the bone and is why a fracture is painful.

Arthrology: joints

Arthrology is the study of joints (articulationes), the places where two or more bones meet. Joints are classified by the tissue that joins the bones:

• Fibrous joints are joined by dense connective tissue and barely move.
  • Sutura: the skull sutures.
  • Gomphosis: a tooth held in its socket by the periodontal ligament.
  • Syndesmosis: bones joined by a ligament or interosseous membrane, such as the radius and ulna.
• Cartilaginous joints are joined by cartilage and allow slight movement.
  • Synchondrosis (primary): hyaline cartilage, such as the epiphyseal growth plate.
  • Symphysis (secondary): fibrocartilage, such as the intervertebral discs and the pubic symphysis.
• Synovial joints have a fluid-filled joint cavity and move freely.

The practicum deck groups the first two together as non-synovial joints (sendi fibrosa in the broad sense), with fibrosa and cartilaginosa as its two branches. The meaning is the same either way.

Types of synovial joint

Books differ on the two-axis joints. The practicum deck treats "condyloid" as the umbrella term and splits it into bicondylar (a convex surface on a concave one, like the knee) and saddle (two perpendicular axes, like the thumb). If a question uses one scheme, answer in that scheme.

Myology: muscles

There are three types of muscle tissue:

A skeletal muscle is described by its attachments:

• Origin: the fixed, usually proximal, attachment.
• Insertion: the movable, usually distal, attachment.
• Action: what the muscle does when it contracts. It pulls the insertion toward the origin.
• Innervation and blood supply: the nerve and artery that serve it.

For every muscle in the limb chapters, learn these four facts together: origin, insertion, innervation and action.

The body systems at a glance

Circulation

Blood flows in two circuits in series:

• Pulmonary circulation: the right ventricle pumps deoxygenated blood through the pulmonary arteries to the lungs; oxygenated blood returns through the pulmonary veins to the left atrium.
• Systemic circulation: the left ventricle pumps oxygenated blood through the aorta and its branches to every tissue; deoxygenated blood returns through the venae cavae to the right atrium.

Arteries carry blood away from the heart and branch like a tree, from the aorta through named arteries into arterioles and capillaries. Veins carry blood back to the heart. In the limbs they form two systems: superficial veins in the subcutaneous tissue (such as the cephalic and great saphenous veins) and deep veins that accompany the arteries and share their names.

Lymphatic system

Lymphatic vessels collect tissue fluid that leaks out of the capillaries and return it to the veins, filtering it through chains of lymph nodes on the way. Most of the body drains to the thoracic duct, which empties at the junction of the left subclavian and left internal jugular veins. The right upper quadrant drains through the right lymphatic duct on the right side.

Nervous system

• Central nervous system (CNS): brain and spinal cord (medulla spinalis).
• Peripheral nervous system (PNS): the cranial and spinal nerves and their ganglia and plexuses.

A few words mean different things in the CNS and PNS:

A single peripheral nerve usually carries both motor (efferent) and sensory (afferent) fibres, which is why one nerve injury can cause both weakness and numbness.

Key teaching point

Anatomy questions reward precision. Describe position from the anatomical position, use the right plane and directional term, and start every name with its type (os, m., a., v., n., lig., art.). Chapters 3 to 7 apply this vocabulary to the skeleton, the head and neck, and the limbs.