Integumentary System: Skin and Its Derivatives

Integumentary System

• The skin, also known as the cutaneous membrane, is the outer covering of the human body and is the largest organ.
• The integumentary system consists of the skin and its derivatives, including nails, hair, sweat glands, and sebaceous glands.

Skin Structure

• The skin is composed of a superficial cellular layer (epidermis) and a deeper connective tissue layer (dermis).
• Skin thickness varies in different parts of the body and is thinner in women than in men.
• The epidermis is thicker in the palms and sole of the feet, while the dermis is thicker on the posterior aspect of the body than anteriorly.

Langer's Lines

• Langer's lines, also known as lines of cleavage, refer to the direction of the rows of collagen in the skin.
• These lines tend to run longitudinally in the limbs and circumferentially in the neck and trunk.
• Incisions parallel to these lines tend to heal with lesser scar formation.

Fasciae

• There are two types of fasciae: superficial and deep.
• Deep fascia includes intermuscular septa, retinacula, bursae, aponeurosis, tendon, tendon sheath, and synovial membrane.

Body Regions

• The human body is partitioned into two main regions: axial and appendicular.
• The axial region includes the head, neck, and trunk, while the appendicular region includes the limbs or appendages.

Body Cavities

• Body cavities are internal chambers that hold vital organs and protect them.
• There are two main body cavities: dorsal and ventral.
• The dorsal body cavity includes the cranial cavity and spinal cavity, while the ventral body cavity includes the thoracic cavity and abdominopelvic cavity.

Thoracic Cavities

• The thoracic cavity contains the heart and lungs.

Terms of Laterality

• Bilateral refers to paired structures having right and left members, such as the kidneys.
• Unilateral refers to structures occurring on one side only, such as the spleen.

Terms of Movement

• Elevation refers to raising or moving a part superiorly.
• Depression refers to lowering or moving a part inferiorly.
• Opposition refers to the movement of the thumb across the palm of the hand to meet another digit pad.
• Reposition refers to the movement of the 1st digit from a position of opposition back to its anatomical position.

Basic Organization of the Body

• A collection of cells of similar morphology performing a specific function is termed tissue.
• There are four basic tissues: epithelium, connective tissue, muscle tissue, and nervous tissue.

Organs and Systems

• An association of different tissues performing a specific function is called an organ.
• A group of organs working harmoniously to discharge a specific function forms a system.
• The human body is composed of several systems, including the integumentary, skeletal, circulatory, digestive, respiratory, urinary, reproductive, nervous, muscular, endocrine, and lymphatic systems.