Organization of the Human Body

Organization of the Human Body

• The human body is composed of several levels of organization:
  • Chemical level: atoms, molecules
  • Cellular level: cells
  • Tissue level: groups of similar cells
  • Organ level: groups of tissues
  • Organ system level: groups of organs
  • Organismal level: the entire human body

Body Cavities

• The human body has several cavities that contain and protect internal organs:
  • Cranial cavity: contains the brain
  • Vertebral cavity: contains the spinal cord
  • Thoracic cavity: contains the heart and lungs
  • Abdominal cavity: contains the digestive organs
  • Pelvic cavity: contains the reproductive organs

Directional Terms

• Directional terms are used to describe the location of body parts in relation to each other:
  • Anterior (front) vs. posterior (back)
  • Superior (above) vs. inferior (below)
  • Medial (middle) vs. lateral (side)
  • Proximal (near the trunk) vs. distal (away from the trunk)

Body Regions

• The human body can be divided into several regions:
  • Head and neck
  • Thorax (chest)
  • Abdomen
  • Pelvis
  • Upper limb (arm)
  • Lower limb (leg)
  • Back

Integumentary System

• The integumentary system is the outermost layer of the body:
  • Skin (epidermis, dermis, hypodermis)
  • Hair
  • Nails
  • Sebaceous and sweat glands

Skeletal System

• The skeletal system provides support and protection for the body:
  • 206 bones in the adult skeleton
  • Bones are classified as:
    • Long bones (e.g. femur, humerus)
    • Short bones (e.g. carpals, tarsals)
    • Flat bones (e.g. ribs, sternum)
    • Irregular bones (e.g. vertebrae, pelvis)

Organization of the Human Body

• The human body is composed of six levels of organization: chemical, cellular, tissue, organ, organ system, and organismal.

Body Cavities

• The human body has five cavities that contain and protect internal organs: cranial, vertebral, thoracic, abdominal, and pelvic cavities.
• The cranial cavity contains the brain, while the vertebral cavity contains the spinal cord.

Directional Terms

• Directional terms describe the location of body parts in relation to each other.
• Anterior refers to the front, while posterior refers to the back.
• Superior refers to above, while inferior refers to below.
• Medial refers to the middle, while lateral refers to the side.
• Proximal refers to near the trunk, while distal refers to away from the trunk.

Body Regions

• The human body can be divided into nine regions: head and neck, thorax, abdomen, pelvis, upper limb, lower limb, and back.

Integumentary System

• The integumentary system is the outermost layer of the body, comprising skin, hair, nails, and sebaceous and sweat glands.
• The skin is composed of three layers: epidermis, dermis, and hypodermis.

Skeletal System

• The skeletal system provides support and protection for the body, composed of 206 bones in the adult skeleton.
• Bones are classified into four types: long bones, short bones, flat bones, and irregular bones.
• Examples of bones include the femur, humerus, carpals, tarsals, ribs, and vertebrae.

Explore the different levels of organization in the human body, from chemical to organismal level, and learn about the various body cavities that protect internal organs.