Introduction to Anatomy: Key Concepts and Structures

Anatomy

The science of the structure and function of the body.

Clinical anatomy

The study of the macroscopic structure and function of the body as it relates to the practice of medicine and other health sciences.

Anatomical Position

Standing erect, upper limbs by the side, and the face and palms of the hands directed anteriorly.

Median Plane

A vertical plane passing through the center dividing into equal right and left halves.

Sagittal Plane

Any plane parallel to the median plane that divides the body into unequal right and left portions.

Coronal (Frontal) Plane

A vertical plane situated at a right angle to the median plane, dividing the body into anterior and posterior portions.

Horizontal Plane

Lies at right angles to both the median and the coronal planes, dividing the body into upper and lower parts.

Transverse Plane

Lies perpendicular to the long axis of a given structure and divides that structure in a cross-sectional orientation.

Anterior (Ventral)

Indicates the front of the body.

Posterior (Dorsal)

Indicates the back of the body.

Medial

Indicates a structure nearer to the median plane of the body than another.

Lateral

Indicates a structure that lies farther away from the median plane of the body than another.

Superior (cranial; cephalic)

Means toward the head end of the body.

Inferior (caudal)

Means away from the head; lower.

Proximal

Describes a position relative to a reference point.

Distal

Describes positions relative to the reference point.

Superficial

Is closer to the surface.

Deep

Is farther away from the surface.

Ipsilateral

Means it's on the same side from the reference point.

Contralateral

Means it's on the opposite side from the reference point.

Supine position

The position of the body lying on the back.

Prone position

The position of the body lying face down.

Flexion

The movement in which a joint angle is decreased (closed) during a motion occurring in a sagittal plane.

Extension

The opposite movement in which the joint angle is increased (opened; straightened) in a sagittal plane.

Dorsiflexion

A special term used to describe the movement of the foot.

Plantarflexion

A special term used to describe the movement of the foot.

Abduction

Movement away from the midline of the body in the coronal plane.

Adduction

Movement toward the midline of the body in the coronal plane.

Inversion

Turning the sole of the foot so the sole faces a medial direction.

Eversion

Turning the sole of the foot so that the sole faces a lateral direction.

Rotation

The movement of a part of the body around its long axis, with little to no movement through space.

Medial (Internal) Rotation

The movement that results in the anterior surface of the part facing medially.

Lateral (External) Rotation

Movement that results in the anterior surface of the part facing laterally.

Circumduction

A complex sequence of movements combining flexion, extension, abduction, adduction, and rotation.

Pronation

Turning the forearm medially in such a manner that the palm of the hand faces posteriorly.

Supination

Turning the forearm laterally from the pronated position so that the palm of the hand comes to face anteriorly.

Protraction

Moving a body part forward.

Retraction

To move a part backward.

Skin

Divided into 2 parts: Epidermis and Dermis.

Epidermis

The outer layer of skin.

Dermis

The inner layer of skin connected to the underlying fascia or bones by the superficial fascia or subcutaneous tissue.

Nails

Keratinized plates on the dorsal surfaces of the tips of the fingers and toes.

Hair Follicles

Structures from which hair grows.

Sebaceous Glands

Glands that secrete sebum.

Sweat Gland

Glands that produce sweat.

Superficial Fascia

Also known as subcutaneous tissue.

Deep Fascia

A type of fascia that may be considerably thickened to form restraining bands.

Skeletal Muscle

Voluntary muscles that attach to bones.

Prime Mover

The chief muscle or member of a chief group of muscles responsible for a particular movement.

Antagonist

Opposes the action of the prime mover.

Fixator

Contracts isometrically to stabilize the origin of the prime mover so that it can act efficiently.

Synergist

Contracts and stabilizes the intermediate joints.

Smooth Muscle

Lines the walls of organs or blood vessels and is involuntary.

Cardiac Muscle

Striated muscle fibers that form the myocardium and conducting system of the heart.

Joints

Sites where two or more bones come together, whether or not movement occurs between them.

Fibrous Joints

Joints where the articulating surfaces of the bones are joined by fibrous tissue, allowing very little movement.

Cartilaginous Joints

Joints united by cartilage, which can be primary or secondary.

Synovial Joints

Joints where the articular surfaces of the bones are covered by a thin layer of hyaline cartilage separated by a joint cavity.

Plane Joints

The opposed articular surfaces are flat or almost flat, and this permits the bones to slide on one another.

Hinge Joints

Resemble the hinge on a door, so that flexion and extension movements are possible.

Pivot Joints

A central bony pivot is surrounded by a bony-ligamentous ring.

Condyloid Joints

Have two distinct convex surfaces that articulate with two concave surfaces, allowing flexion, extension, abduction, and adduction together with a small amount of rotation.

Ellipsoid Joints

An elliptical convex articular surface fits into an elliptical concave articular surface, allowing flexion, extension, abduction, and adduction, but rotation is impossible.

Saddle Joints

The articular surfaces are reciprocally concave convex and resemble a saddle on a horse's back, permitting flexion, extension, abduction, adduction, and rotation.

Ball and Socket Joints

Ball shaped head of one bone fits into a socket like concavity of another, permitting free movements including flexion, extension, abduction, adduction, medial rotation, lateral rotation, and circumduction.

Stability of Joints

Three main factors: shape, size, and arrangement of articular surfaces; ligaments; tone of muscles around the joint.

Hilton's Law

States that often a nerve that innervates a joint also tends to innervate the muscles that move the joint and the skin that covers the attachments of those muscles.

Ligaments

A cord or band of connective tissue uniting two structures, most are dense bundles of collagen, unstretchable.

Bursae

A lubricating device consisting of a closed fibrous sac lined with a delicate smooth membrane.

Synovial Sheath

A tubular bursa that surrounds a tendon.

Blood Vessels

Three Types: Arteries, Veins, and capillaries.

Arteries

Transport blood away from the heart and are valve-less.

Veins

Transport blood towards the heart and contain valves.

Capillaries

Microscopic vessels in the form of a network connecting the arterioles to the venules.

Sinusoids

Similar to capillaries but larger and irregular.

Portal System

A system of vessels interposed between two capillary beds.

Anastomosis

The joining of branches of arteries, allowing collateral circulation.

Lymphatic System

Consists of lymphatic tissues and lymphatic vessels.

Lymphatic Tissues

Contains a large number of lymphocytes, including Thymus, Lymph Nodes, Spleen, and Lymphatic Nodules.

Lymph

Fluid in lymphatic vessels.

Lymphatic Capillaries

A network of fine vessels that drain lymph from the tissues.

Afferent Vessels

The lymph vessels that carry lymph to a lymph node.

Efferent Vessels

Transport lymph away from a node.

Right Lymphatic Duct

The lymph reaches the bloodstream at the root of the neck by large lymph vessels.

Central Nervous System

Composed of large numbers of nerve cells and their processes, supported by specialized tissue called neuroglia.

Neuron

The term given to the nerve cell and its processes.

Processes of Neuron

Two types: dendrites and axon.

Dendrites

Short process of the cell body.

Axon

Long process of the cell body.

Gray matter

Consists of nerve cells and cell bodies embedded in neuroglia.

White matter

Consists of nerve fibers (axons) embedded in neuroglia (transmits impulses to farther distance from brain).

Peripheral Nervous System

Cranial nerves and spinal nerves and their associated ganglia.

Cranial Nerves

12 pairs of cranial nerves that leave the brain and pass through foramina in the skull.

Spinal Nerves

A total of 31 pairs of spinal nerves leave the spinal cord through intervertebral foramina in the vertebral column.

Cervical Nerves

8 pairs of spinal nerves associated with the cervical vertebrae.

Thoracic Nerves

12 pairs of spinal nerves associated with the thoracic vertebrae.

Lumbar Nerves

5 pairs of spinal nerves associated with the lumbar vertebrae.

Sacral Nerves

5 pairs of spinal nerves associated with the sacral vertebrae.

Coccygeal Nerve

1 pair of spinal nerves associated with the coccyx.

Cauda Equina

Bundle of nerves that resembles a horse's tail, termination of spinal cord.