Introduction to Human Anatomy

• Human anatomy is the scientific study of the structure of the human body.

Levels of Organization

• Atoms combine to form molecules at the chemical level.
• Molecules form organelles, such as the nucleus and mitochondria, which make up cells at the cellular level.
• Similar cells and surrounding materials make up tissues at the tissue level.
• Different tissues combine to form organs at the organ level.
• Organs working together to perform specific functions form organ systems at the system level.
• Organ systems working together create the whole organism at the organism level.

Anatomical Position

• The standard anatomical position is a reference point for describing the human body.
• The body is standing erect, facing forward, with feet together, arms hanging at the sides, and palms facing forward.

Anatomical Directions

• Superior (cranial): Toward the head end or upper part of a structure or the body; above.
• Inferior (caudal): Away from the head end or toward the lower part of a structure or the body; below.
• Anterior (ventral): Toward the front of the body; in front of.
• Posterior (dorsal): Toward the back of the body; behind.
• Medial: Toward the midline of the body; on the inner side of.
• Lateral: Away from the midline of the body; on the outer side of.
• Proximal: Closer to the origin of the body part or the point of attachment of a limb to the body trunk.
• Distal: Farther from the origin of a body part or the point of attachment of a limb to the body trunk.

Anatomical Planes

• Sagittal plane: Divides the body into right and left parts.
• Midsagittal (median) plane: Sagittal plane that lies exactly in the midline.
• Frontal (coronal) plane: Divides the body into anterior and posterior parts.
• Transverse (horizontal) plane: Divides the body into superior and inferior parts.
• Oblique section: Cuts made diagonally.

Body Cavities

• Dorsal body cavity: Protects the fragile nervous system organs.
• Cranial cavity: Within the skull and encases the brain.
• Vertebral cavity: Runs through the vertebral column to enclose the spinal cord.
• Ventral body cavity: More anterior and larger than the dorsal cavity.
• Thoracic cavity: Surrounded by the ribs and muscles of the chest.
• Pleural cavities: Each enveloping a lung.
• Mediastinum: Contains the pericardial cavity and surrounds the remaining thoracic organs (esophagus, trachea).
• Pericardial cavity: Encloses the heart.
• Abdominopelvic cavity: Inferior to the thoracic cavity.
• Abdominal cavity: Contains the stomach, intestines, spleen, liver, and other organs.
• Pelvic cavity: Lies within the bony pelvis and contains the urinary bladder, reproductive organs, and rectum.

Integumentary System

• Consists of the skin, hair, nails, and cutaneous glands.
• Functions:
  • Protection
  • Temperature regulation
  • Sensation
  • Vitamin D synthesis
  • Excretion

Skeletal System

• Consists of bones, cartilage, and ligaments.
• Functions:
  • Support
  • Movement
  • Protection
  • Blood cell production
  • Mineral storage

Muscular System

• Consists of skeletal muscles.
• Functions:
  • Movement
  • Posture
  • Heat production

Nervous System

• Consists of the brain, spinal cord, nerves, and sensory receptors.
• Functions:
  • Control
  • Communication
  • Coordination
  • Sensation

Endocrine System

• Consists of glands that secrete hormones.
• Functions:
  • Hormone production
  • Regulation of body activities (growth, reproduction, metabolism)

Cardiovascular System

• Consists of the heart, blood vessels, and blood.
• Functions:
  • Transport of nutrients, oxygen, and waste products
  • Immune response

Lymphatic System

• Consists of lymphatic vessels, lymph nodes, and lymphoid organs.
• Functions:
  • Fluid recovery
  • Immunity

Respiratory System

• Consists of the lungs, trachea, and associated structures.
• Functions:
  • Gas exchange (intake of oxygen and elimination of carbon dioxide)

Digestive System

• Consists of the mouth, esophagus, stomach, intestines, and accessory organs.
• Functions:
  • Nutrient breakdown and absorption
  • Elimination of waste

Urinary System

• Consists of the kidneys, ureters, urinary bladder, and urethra.
• Functions:
  • Waste elimination
  • Fluid and electrolyte balance

Reproductive System

• Male: Consists of testes, ducts, and penis.
• Female: Consists of ovaries, uterine tubes, uterus, and vagina.
• Functions:
  • Production of offspring

Tissues

• Epithelial tissue: Covers body surfaces and lines body cavities.
• Connective tissue: Supports, connects, and separates different types of tissues and organs in the body.
• Muscle tissue: Contracts to produce movement.
• Nervous tissue: Conducts electrical signals.

Bones

• Long bones: Longer than they are wide (e.g., femur, humerus).
• Short bones: Cube-shaped (e.g., carpals, tarsals).
• Flat bones: Thin, flattened, and usually curved (e.g., skull bones, ribs).
• Irregular bones: Complex shapes (e.g., vertebrae, hip bones).

Joints

• Fibrous joints: Immovable or slightly movable (e.g., sutures of the skull).
• Cartilaginous joints: Slightly movable (e.g., intervertebral discs).
• Synovial joints: Freely movable (e.g., knee, shoulder).

Muscles

• Skeletal muscle: Voluntary, striated.
• Smooth muscle: Involuntary, non-striated.
• Cardiac muscle: Involuntary, striated.

Nerves

• Sensory (afferent) nerves: Carry signals from sensory receptors to the central nervous system.
• Motor (efferent) nerves: Carry signals from the central nervous system to muscles and glands.
• Mixed nerves: Contain both sensory and motor fibers.

Arteries and Veins

• Arteries: Carry blood away from the heart.
• Veins: Carry blood to the heart.
• Capillaries: Tiny vessels where exchange of nutrients and wastes occurs.

Lymph Nodes

• Filter lymph and play a role in the immune system.

Endocrine Glands

• Pituitary gland: Regulates growth and other endocrine glands.
• Thyroid gland: Regulates metabolism.
• Adrenal glands: Produce hormones involved in stress response.
• Pancreas: Regulates blood sugar.
• Ovaries/Testes: Produce sex hormones.

Heart

• Four chambers:
  • Right atrium
  • Right ventricle
  • Left atrium
  • Left ventricle

Brain

• Cerebrum: Responsible for higher-level cognitive functions.
• Cerebellum: Coordinates movement and balance.
• Brainstem : Controls basic life functions.

Lungs

• Site of gas exchange (oxygen and carbon dioxide).

Stomach

• Stores food and begins chemical digestion.

Small Intestine

• Completes digestion and absorbs nutrients.

Large Intestine

• Absorbs water and forms feces.

Kidneys

• Filter blood and produce urine.