Organization of the Human Body

Organization of the Body

• The human body is organized into several levels, from simplest to most complex:
  1. Chemical level: atoms, molecules
  2. Cellular level: cells, the basic structural and functional units of the body
  3. Tissue level: groups of similar cells performing a specific function
  4. Organ level: structures composed of two or more types of tissues
  5. Organ system level: groups of organs working together to perform a specific function
  6. Organismal level: the entire human body

Body Cavities

• The body has several cavities that provide protection and support for internal organs:
  • Cranial cavity: contains the brain
  • Thoracic cavity: contains the heart, lungs, and major blood vessels
  • Abdominal cavity: contains the digestive organs
  • Pelvic cavity: contains the reproductive organs and urinary bladder

Directional Terms

• Used to describe the location of body structures:
  • Anterior (front) vs. posterior (back)
  • Superior (upper) vs. inferior (lower)
  • Medial (toward the midline) vs. lateral (away from the midline)
  • Proximal (near the trunk) vs. distal (away from the trunk)
  • Superficial (near the surface) vs. deep (away from the surface)

Body Regions

• Divided into several regions:
  • Head: includes the face, cranium, and brain
  • Neck: connects the head to the thorax
  • Thorax: contains the chest and upper back
  • Abdomen: contains the digestive organs
  • Pelvis: contains the reproductive organs and urinary bladder
  • Upper limb: includes the arm, forearm, and hand
  • Lower limb: includes the thigh, leg, and foot

Organization of the Body

• The human body is organized into six levels of complexity, ranging from simplest to most complex: atoms, cells, tissues, organs, organ systems, and the entire organism.
• Chemical level consists of atoms and molecules.
• Cellular level is made up of cells, the basic structural and functional units of the body.
• Tissue level consists of groups of similar cells performing a specific function.
• Organ level consists of structures composed of two or more types of tissues.
• Organ system level consists of groups of organs working together to perform a specific function.
• Organismal level refers to the entire human body.

Body Cavities

• The body has four main cavities that provide protection and support for internal organs.
• Cranial cavity contains the brain.
• Thoracic cavity contains the heart, lungs, and major blood vessels.
• Abdominal cavity contains the digestive organs.
• Pelvic cavity contains the reproductive organs and urinary bladder.

Directional Terms

• Directional terms are used to describe the location of body structures.
• Anterior refers to the front of the body.
• Posterior refers to the back of the body.
• Superior refers to the upper part of the body.
• Inferior refers to the lower part of the body.
• Medial refers to the midline of the body.
• Lateral refers to the sides of the body.
• Proximal refers to the part of the body closest to the trunk.
• Distal refers to the part of the body farthest from the trunk.
• Superficial refers to the surface of the body.
• Deep refers to the internal parts of the body.

Body Regions

• The body can be divided into several regions.
• The head includes the face, cranium, and brain.
• The neck connects the head to the thorax.
• The thorax contains the chest and upper back.
• The abdomen contains the digestive organs.
• The pelvis contains the reproductive organs and urinary bladder.
• The upper limb includes the arm, forearm, and hand.
• The lower limb includes the thigh, leg, and foot.