Anatomical Position, Terms, and Movements

• Introduction to anatomical position, terms and movements

What is Anatomy?

• Anatomy studies the structure of animals or plants.
• Human anatomy studies the structure of the human organism.
• The word "anatomy" originates from the Greek term "anatome," signifying "cutting up." Its Latin equivalent is "dissectio".
• Modern anatomy encompasses a broader scope than just cutting up.
• Anatomy provides the foundation for the art of medicine and introduces students to medical terminology.

Branches of Anatomy

• Gross or macroscopic anatomy involves studying the structure of an organism with the naked eye and through dissection.
• Microscopic anatomy (cytology and histology) studies the body's structure using a microscope.
• Histochemistry studies the chemical composition of cells and tissues.
• Embryology studies changes from fertilization to birth.
• Comparative anatomy studies relationships between structures of related organisms.

Methods of Studying Anatomy

• Regional or topographical anatomy studies the body's structure by region such as the upper limb, thorax, abdomen, pelvis, lower limb, head, and neck.
• Surface anatomy studies external features of an organism and is essential to regional anatomy.
• Systemic anatomy studies organisms by systems, including the respiratory, circulatory, skeletal (osteology), gastrointestinal, reproductive, and nervous systems.
• Clinical or applied anatomy studies the structure and function of the body as it relates to medical practices and other health sciences.
• Radiological anatomy studies anatomy using imaging modalities like X-rays, computed tomography (CT), and magnetic resonance imaging (MRI).

History of Anatomy

• Formal anatomical studies began in Egypt around 500 BC.
• Hippocrates of Cos (460-377 BC) is considered the father of medicine and a founding father of anatomy.
• Herophilus of Alexandria (325-255 BC) is regarded as the founding father of anatomy as a systematic discipline.
• Aristotle (384-322 BC) is regarded as the founder of comparative anatomy.
• Leonardo da Vinci (1452-1519) was an anatomist and artist. He created accurate models and paintings of the human body.
• Andreas Vesalius (1514-1564) systematically studied human body structure and corrected over 200 anatomical errors made by Galen.

Discoveries by medical students

• Sinoatrial node was discovered by Martin Flack
• Islets of pancreas was discovered by Langerhans
• Collecting tubules of kidney was discovered by Bellini
• Parotid duct was discovered by Stensen
• Venae cordis minimae was discovered by Thebesius

Anatomical Terms

• Anatomical terminology follows the International Anatomical Terminology and makes up a large part of medical terminology.
• The anatomical position is defined as standing erect with eyes directed straight ahead, arms at the sides, palms facing forward, and toes together pointing forward, and anatomical descriptions are based on this position.

Anatomical Planes

• Median or midsagittal plane: Imaginary vertical plane dividing the body into right and left halves, meeting anterior and posterior surfaces at the midlines.
• Sagittal plane: Imaginary vertical anteroposterior plane dividing the body into right and left parts (not halves), and parallel to the median plane, named after the sagittal suture of the skull.
• Coronal or frontal plane: Vertical plane from side to side dividing the body into anterior and posterior parts, intersecting the median plane at right angles, and named after the coronal suture of the skull.
• Horizontal, transverse, or axial plane: Imaginary plane dividing the body into upper and lower parts, at right angles to both median and coronal planes.

Sections

• Longitudinal section: A section of an organ that passes through its long axis.
• Transverse or cross-section: A section of an organ at right angles to its long axis.
• Oblique section: A section that is neither longitudinal nor horizontal.

Lines of the Body

• Anterior median or midsternal line: The intersection of the median plane with the anterior surface of the thorax.
• Posterior median or midvertebral line: The intersection of the median plane with the posterior surface of the thorax or vertebral column.
• Midclavicular or lateral vertical or mammary line: A vertical line that passes through the midpoint of the clavicle, reaching the midinguinal point, and is parallel to the anterior median line.
• Anterior axillary line: A vertical line that passes through the anterior axillary fold, formed by the border of the pectoralis major.
• Midaxillary line: Line passing through the apex of the axilla, parallel to the anterior and posterior axillary lines.
• Posterior axillary line: A vertical line along the posterior axillary fold formed by the latissimus dorsi and teres major muscles.
• Lateral sternal line: Passes along the sternal margin.
• Parasternal line: Midway between the lateral sternal and midclavicular lines.

Terms of Relationship

• Anterior: Nearer to the front surface of the body.
• Posterior: Nearer to the back surface of the body.
• Superior: Nearer to the top or upper end of the body or the crown of the head.
• Inferior: Nearer to the lower end or the sole of the foot.
• Medial: Nearer to the median plane.
• Lateral: Farther from the median plane.
• Ipsilateral: On the same side of the body.
• Contralateral: On the opposite side of the body.

Trunk Terms

• Ventral: Nearer to the front of the trunk.
• Dorsal: Nearer to the back of the trunk.
• Cephalic or cranial: Nearer to the head.
• Caudal: Nearer to the tail end.
• Rostral: Nearer to the front end; in the postembryonic period, this is the region around the nose and mouth.
• Anterior and ventral are synonymous when referring to the trunk, and posterior and dorsal are also interchangeable.

Additional Terms

• Internal: Nearer to the center of an organ or cavity.
• External: Farther from the center of an organ or cavity.
• Superficial: Nearer to the skin or surface of the body.
• Deep: Farther from the surface of the body.
• Invagination: Inward bulging of the wall of a cavity.
• Evagination: Outward bulging of the wall of a cavity.
• Proximal: Nearer to the root or attached end of the trunk.
• Distal: Farther from the root or attached end of the trunk.
• Preaxial border: The thumb or big toe side of a limb; lateral or radial side in the upper limb, medial or tibial border in the lower limb.
• Postaxial border: Opposite of the preaxial border.

Terms of Movements

• Flexion: Bending or moving forward.
• Extension: Straightening or moving backward.
• Adduction: Movement toward the median plane.
• Abduction: Movement away from the median plane.
• In the upper limb, the middle finger lies in the axial line of the hand. Ulnar deviation = adduction; radial deviation = abduction. In the lower limb the 2nd toe lies in the axial line
• Circumduction: A sequence of movements involving flexion, abduction, extension, and adduction.
• Rotation: Movement in which a body part is turned around its own long axis, can be medial (internal) or lateral (external).
• Pronation: Rotating the forearm medially so the palm faces posteriorly (blessing).
• Supination: Rotating the forearm laterally so the palm faces anteriorly (begging).
• Supine position: The body lies on its back.
• Prone position: The body lies face down.
• Protraction: Forward movement.
• Retraction: Backward movement.

Anatomical Terms

• Humerus = Shoulder
• Axilla = Armpit
• Brachium = Arm
• Cubitus = Elbow
• Antebrachium = Forearm
• Carpus = Wrist
• Manus = hand
• Palma = palm
• Digitus manus = finger
• Pollex (digitus primus) = thumb
• D indicis = index finger
• Digitus medius = middle finger
• Digitus annularis = ring finger
• Digitus minimus = Little finger
• Brevis = short
• Longus = long
• Superficialis (sublimis) = superficial
• Profundus = deep
• Capitatie = head-like
• Scaphoid = like a small boat
• Hamate = hook
• Glenoid = Socket-like
• Trochlear = Pulley-like

Bones of the Should Girdle

• The clavicle and scapula are the bones of the shoulder girdle.
• The clavicle connects the upper limb to the trunk and transmits part of the weight of the upper limb to the sternum.
• It acts as a strut allowing the arm to swing away from the trunk. The clavicle is a long bone with a shaft and two ends.
• The medial or sternal end is thickened and quadrangular in shape and articulates with the manubrium of the sternum and the first costal cartilage.
• The lateral or acromial end is flattened and articulates with the acromion of the scapula.
• The shaft has two curves: the medial two-thirds is convex anteriorly, and the lateral one-third is concave anteriorly, giving the clavicle an elongated capital S appearance.
• The medial two-thirds is rounded with four surfaces (anterior, posterior, superior, inferior); the anterior surface gives origin to the clavicular head of the pectoralis major muscle.
• The sternohyoid muscle arises from the posterior surface close to the sternal end.
• The superior surface gives origin to the clavicular head of the sternocleidomastoid (arising from the medial third of the superior surface).
• The inferior surface has a rough oval impression at its medial end for the costoclavicular ligament.
• The rhomboid fossa is the impression which also has a rough impression on its lateral part for the attachment of the coracoclavicular ligament, and a longitudinal groove in its middle for the insertion of subclavius.
• The clavipectoral fascia attaches to the margins of the grove.
• The lateral one-third is flattened, with anterior and posterior borders, and superior and inferior surfaces.
• The anterior border gives origin to the deltoid muscle, while the posterior border is for the insertion of the trapezius.
• The superior surface is smooth, while the inferior surface has an elevation near its posterior border called the conoid tubercle and a ridge called the trapezoid ridge.
• The conoid tubercle and trapezoid ridge give attachment to the conoid and trapezoid parts of the coracoclavicular ligament.
• The clavicle is shorter, smoother, thinner, lighter, and less curved in females than in males whilst the right clavicle is shorter and stronger than the left.
• The clavicle may be congenitally absent

Ossification of the Clavicle

• The clavicle is the first bone to begin ossifying and ossifies in the membrane, except for its medial end, which ossifies in cartilage.
• It has three centers of ossification: two primary and one secondary.
• The two primary centers appear in the shaft in the 5th or 6th week and fuse at about the 45th day
• The secondary center appears at the medial end around the 15th year in females and the 17th year in males, fusing with the shaft around the 25th year, sometimes with another secondary center at the acromial end

Peculiarities of the Clavicle

• It is the first bone to begin to ossify and the last to complete ossification.
• It is the only long bone that has two primary centers of ossification.
• It is the only long bone that ossifies in membrane.
• It is the only long bone that lies horizontally.
• It is subcutaneous throughout its length.
• It does not usually have a medullary cavity.
• It is the most commonly fractured bone in the body, usually at the junction between the middle and lateral thirds of the clavicle
• When there is a fracture medial to the coracoclavicular ligament, the lateral end of the clavicle is pulled down by the weight of the upper limb, while the medial end is only slightly deformed because of the balanced action of pectoralis major and sternocleidomastoid.
• It is sometimes pierced by a branch of the supraclavicular nerve.