Human Anatomy and Physiology Essentials: Homeostasis, Blood, Joints, Skin

Homeostasis and Examples

Homeostasis is the ability of the body to maintain a stable internal environment despite changes in the external environment. Examples include: 1) body temperature regulation, 2) blood glucose regulation, 3) water balance, 4) blood pressure regulation, and 5) pH balance.

Branches: Anatomy and Physiology

Anatomy is the branch of science that deals with the study of the structure of different organisms and the human body.

Physiology is the branch of science that deals with the study of the functions of different organisms and the human body.

Cell and Tissue Structure and Function

Cell is the smallest structural and functional unit of the living body that carries out all vital physiological activities.

Tissue is a group of similar cells having a common origin, along with intercellular substance, that work together to perform a specific function.

Functions of Blood

Function of blood:

1. Transport — Blood transports oxygen (O2) from the lungs to the cells and carbon dioxide (CO2) from the cells to the lungs; transports nutrients from the digestive organs to the cells; transports hormones and enzymes to target tissues and glands; and transports waste products from body cells to the kidneys, lungs, and sweat glands.
2. Regulation — Blood helps regulate body pH through buffers, regulates body temperature via the heat-absorbing and cooling properties of its water content, and helps regulate water balance.
3. Protection — Blood protects the body against blood loss through its clotting mechanisms, and protects against pathogens via phagocytes, white blood cells (WBCs), and antibodies.

Joints and Types

Joint — A joint (also called an articulation) is the connection between two bones in which one bone is attached to another.

Types of joints: fibrous joints, cartilaginous joints, and synovial joints.

Fibrous Joints

Fibrous joints are immovable (synarthroses). They are fixed joints where bones are joined by fibrous connective tissue. Example: cranial sutures between bones of the skull.

Cartilaginous Joints

Cartilaginous joints are slightly movable (amphiarthroses). Bones are connected by cartilage and allow little or no movement. Example: pubic symphysis.

Synovial Joints

Synovial joints are the most common type of joint and are freely movable (diarthroses). These joints enable activities such as walking and running and allow movement in one or more directions.

Classification of Synovial Joints

• Ball-and-socket joint — Allows the greatest range of movement; one bone fits into the socket of another. Examples: shoulder and hip joints.
• Hinge joint — Allows movement in one plane (flexion and extension). Examples: elbow, knee, and interphalangeal joints.
• Saddle joint — A biaxial, movable joint with complementary saddle-shaped surfaces. Example: carpometacarpal joint of the thumb.
• Pivot joint — Permits rotation around a single axis. Examples: atlantoaxial joint (between the first two cervical vertebrae) and the proximal radioulnar joint.
• Gliding joint — Occurs between the flat surfaces of bones that glide over one another, held together by ligaments. Examples: intercarpal, intertarsal, and facet (vertebral) joints.
• Condyloid (ellipsoid) joint — Allows movement around two axes (biaxial). Example: metacarpophalangeal joints (knuckle joints) between metacarpals and phalanges.

Skin: Structure and Layers

The skin is the outer covering of the body. In humans, it is the largest organ of the integumentary system. Skin accounts for approximately 12–15% of total body weight. The thickness of skin varies from about 0.05 mm on the eyelids to about 4.0 mm on the sole of the foot.

Layers of Skin

Epidermis, Dermis, Hypodermis.

Epidermis

The epidermis is the outermost layer of the skin. It is composed primarily of keratinocytes, which produce the protein keratin and form a protective barrier.