BASIC CONCEPTS OF ANATOMY-1

LANGUAGE OF ANATOMY

Various positions, planes, terms in relation to various regions and movements are described.

POSITIONS :

• Anatomical position: When a person is standing straight with eyes looking forwards, both arms by the side of body, palms facing forwards, both feet together, the position is anatomical position.

• Supine position: When a person is lying on her/his back, arms by the side, palms facing upwards and feet put together, the position is supine position.

• Prone position: Person lying on his/her face, chest and abdomen is said to be in prone position.

• Lithotomy position: Person lying on her back with legs up and feet supported in straps. This position is mostly used during delivery of the baby.

PLANES :

• A plane passing through the centre of the body dividing it into two equal right and left halves, is the median or midsagittal plane.
• Plane parallel to median or midsagittal plane is the sagittal plane.
• A plane at right angles to sagittal or median plane which divides the body into anterior and posterior halves is called a coronal plane.
• A plane at right angles to both sagittal and coronal planes which divides the body into upper and lower parts is called a transverse plane.

TERMS USED IN RELATION TO TRUNK :

• Ventral or Anterior is the front of trunk.
• Dorsal or Posterior is the back of trunk.
• Medial is a plane close to the median plane.
• Lateral is plane away from the median plane.
• Proximal/Cranial/Superior is close to the head end of trunk.
• Distal/Caudal/Inferior is close to the lower end of the trunk.
• Superficial is close to skin/towards surface of body.
• Deep away from skin/away from surface of body.
• Ipsilateral on the same side of the body as another structure.
• Contralateral on opposite side of body from another structure.
• Invagination is projection inside.
• Evagination is projection outside.

TERMS USED IN RELATION TO UPPER LIMB :

• Ventral or Anterior is the front aspect.
• Dorsal or Posterior is the back aspect.
• Medial border lies along the little finger, medial border of forearm and arm.
• Lateral border follows the thumb, lateral border of forearm and arm.
• Proximal is close to root of limb, while distal is away from the root.
• Palmar aspect is the front of the palm.
• Dorsal aspect of hand is on the back of palm.
• Flexor aspect is front of upper limb.
• Extensor aspect is back of upper limb.

TERMS USED IN RELATION TO LOWER LIMB :

• Posterior aspect is the back of lower limb.
• Anterior aspect is front of lower limb.
• Medial border lies along the big toe or hallux, medial border of leg and thigh.
• Lateral border lies along the little toe, lateral border of leg and thigh.
• Flexor aspect is back of lower limb.
• Extensor aspect is front of lower limb.
• Proximal is close to the root of limb, while distal is away from it.

TERMS OF RELATION COMMONLY USED IN EMBRYOLOGY & COMPARATIVE ANATOMY, BUT SOMETIMES IN GROSS ANATOMY :

• Ventral - Towards the belly (like anterior).
• Dorsal - Towards the back (like posterior).
• Cranial or Rostral - Towards the head (like superior).
• Caudal - Towards the tail.

TERMS RELATED TO BODY MOVEMENTS :

Movements in general at synovial joints are divided into four main categories.

Gliding movement: Relatively flat surfaces move back-andforth and from side-to-side with respect to one another. The angle between articulating bones does not change significantly.

Angular movements: Angle between articulating bones decreases or increases. In flexion there is decrease in angle between articulating bones and in extension there is increase in angle between articulating bones. Lateral flexion is movement of trunk sideways to the right or left at the waist. Adduction is movement of bone toward midline whereas abduction is movement of bone away from midline.

Rotation: A bone revolves around its own longitudinal axis. In medial rotation anterior surface of a bone of limb is turned towards the midline. In lateral rotation anterior surface of bone of limb is turned away from midline.

Special movements: These occur only at certain joints, e.g. pronation, supination at radioulnar joints, protraction and retraction at temporo-mandibular joint.

In Upper limb

• Flexion: When two flexor surfaces are brought close to each other, e.g. in elbow joint when front of arm and forearm are opposed to each other.
• Extension: When extensor or dorsal surfaces are brought in as much approximation as possible, e.g. straighten the arm and forearm at the elbow joint.
• Abduction: When limb is taken away from the body.
• Adduction: When limb is brought close to the body.
• Circumduction: It is movement of distal end of a part of the body in a circle. A combination of extension, abduction, flexion and adduction in a sequence is called circumduction as in bowling.
• Medial rotation: When the arm rotates medially bringing the flexed forearm across the chest.
• Lateral rotation: When arm rotates laterally taking the flexed forearm away from the body.
• Supination: When the palm is facing forwards or upwards, as in putting food in the mouth.
• Pronation: When the palm faces backwards or downwards, as in picking food with fingers from the plate.
• Adduction of digits/fingers: When all the fingers get together.
• Abduction: When all fingers separate. The axis of movement of fingers is the line passing through the centre of the middle finger.
• Opposition of thumb: When tip of thumb touches the tips of any of the fingers.
• Circumduction of thumb: Movement of extension, abduction, flexion and adduction in sequence.

In Lower Limb

• Flexion of thigh: When front of thigh comes in contact with front of abdomen.
• Extension of thigh: When person stands erect.
• Abduction: When thigh is taken away from the median plane.
• Adduction: When thigh is brought close to median plane.
• Medial rotation: When thigh is turned medially.
• Lateral rotation: When thigh is turned laterally.
• Flexion of knee: When back of thigh and back of leg come in opposition.
• Extension of knee: When thigh and leg are in straight line as in standing.
• Dorsiflexion of foot: When dorsum of foot is brought close to front of leg and sole faces forwards.
• Plantarflexion of foot: When sole of foot or plantar aspect of foot faces backwards.
• Inversion of foot: When medial border of foot is raised from the ground.
• Eversion of foot: When lateral border of foot is raised from the ground.

In the Neck

• Flexion: When face comes closer to chest.
• Extension: When face is brought away from the chest
• Lateral flexion: When ear is brought close to shoulder.
• Rotation: When neck rotates so that chin goes to opposite side.
• Opening the mouth: When lower jaw is lowered to open the mouth.
• Closure of the mouth: When lower jaw is opposed to the upper jaw, closing the mouth.
• Protraction: When lower jaw slides forwards in its socket in the temporal bone of skull.
• Retraction: When lower jaw slides backwards in its socket in the temporal bone of skull.

In the Trunk

• Backward bending is called extension.
• Forward bending is flexion.
• Sideward movement is lateral flexion.
• Sideward rotation is lateral rotation.

TERMS USED FOR DESCRIBING MUSCLES :

• Origin: The end of a muscle which is relatively fixed during its contraction.
• Insertion: The end of a muscle which moves during its contraction. The two terms, origin and insertion, are sometimes interchangeable, when the origin moves and the insertion is fixed.
• Belly: The fleshy and contractile part of a muscle.
• Tendon: The fibrous noncontractile and cord-like part of a muscle.
• Aponeurosis: The flattened tendon.
• Raphe: A fibrous band made up of interdigitating fibres of the tendons or aponeuroses. Unlike a ligament, it is stretchable. Ligaments are fibrous, inelastic bands which connect two segments of a joint.

TERMS USED IN DESCRIBING VESSELS : 

• Arteries carry oxygenated blood away from the heart, with the exception of the pulmonary and umbilical arteries which carry deoxygenated blood. Arteries resemble trees because they have branches (arterioles).
• Veins carry deoxygenated blood towards the heart, with the exception of the pulmonary and umbilical veins which carry oxygenated blood. Veins resemble rivers because they have tributaries (venules). Veins have valves to allow unidirectional flow of blood.
• Capillaries are networks of microscopic vessels connecting arterioles to venules.
• Anastomosis is a precapillary or postcapillary communication between the neighbouring vessels.

TERMS USED FOR DESCRIBING BONE FEATURES :

• Linear elevation may be a line, lip, ridge, or crest.
• Sharp elevation may be a spine, styloid process, cornu (horn), or hamulus.
• Rounded or irregular elevation may be a tubercle, tuberosity, epicondyle, malleolus, or trochanter. A ramus is a broad arm or process projecting from the main part or body of the bone.
• Depressions may be a pit, impression, fovea, fossa, groove(sulcus), or notch (incisura).
• Openings may be a foramen, canal, hiatus, or aqueduct.
• Cavities: A large cavity within a bone is called sinus, cell or antrum.
• Smooth articular areas may be a facet, condyle, head, capitulum, or trochlea.