Human Anatomy: Terminology and Body Planes

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

Anatomical Terminology

• Anatomical terms provide a standardized language for describing the human body.
• Anatomical position: The body is erect, feet forward, arms at the sides, palms facing forward, and thumbs pointing away from the body.
• Anterior (ventral): Toward the front of the body.
• Posterior (dorsal): Toward the back of the body.
• Superior (cranial): Toward the head or above.
• Inferior (caudal): Toward the feet or below.
• Medial: Toward the midline of the body.
• Lateral: Away from the midline of the body.
• Proximal: Closer to the point of attachment or origin.
• Distal: Farther from the point of attachment or origin.
• Superficial: Closer to the surface of the body.
• Deep: Away from the surface of the body.

Body Planes

• Sagittal plane: Divides the body into right and left parts.
• Midsagittal plane: Divides the body into equal right and left halves.
• Frontal (coronal) plane: Divides the body into anterior and posterior parts.
• Transverse (horizontal) plane: Divides the body into superior and inferior parts.

Body Cavities

• Body cavities are spaces within the body that contain and protect internal organs.
• Dorsal body cavity: Contains the cranial cavity and the vertebral canal.
  • Cranial cavity: Encloses the brain.
  • Vertebral canal: Encloses the spinal cord.
• Ventral body cavity: Contains the thoracic cavity and the abdominopelvic cavity.
  • Thoracic cavity: Contains the pleural cavities (lungs) and the mediastinum.
  • Mediastinum: Contains the pericardial cavity (heart) and other structures.
  • Abdominopelvic cavity: Contains the abdominal cavity and the pelvic cavity.
  • Abdominal cavity: Contains the stomach, intestines, liver, and other organs.
  • Pelvic cavity: Contains the bladder, reproductive organs, and rectum.

Skeletal System

• The skeletal system provides support, protection, movement, mineral storage, and blood cell formation.
• Bones: There are 206 bones in the adult human body.
• Axial skeleton: Consists of the skull, vertebral column, and rib cage.
• Appendicular skeleton: Consists of the bones of the limbs and their girdles.
• Bone structure:
  • Compact bone: Dense outer layer.
  • Spongy bone: Inner layer with trabeculae.
  • Bone marrow: Red (blood cell formation) and yellow (fat storage).
• Joints:
  • Fibrous: Immovable (e.g., sutures of the skull).
  • Cartilaginous: Slightly movable (e.g., intervertebral discs).
  • Synovial: Freely movable (e.g., knee joint).
• Types of synovial joints:
  • Ball-and-socket (e.g., hip).
  • Hinge (e.g., elbow).
  • Pivot (e.g., radioulnar).
  • Gliding (e.g., intercarpal).
  • Condyloid (e.g., radiocarpal).
  • Saddle (e.g., carpometacarpal of the thumb).

Muscular System

• The muscular system enables movement, maintains posture, and generates heat.
• Types of muscle tissue:
  • Skeletal muscle: Voluntary, striated.
  • Smooth muscle: Involuntary, non-striated.
  • Cardiac muscle: Involuntary, striated (heart).
• Skeletal muscle structure:
  • Muscle fibers (cells).
  • Myofibrils (contractile units).
  • Sarcomeres (functional units of myofibrils).
  • Actin and myosin filaments.
• Muscle contraction:
  • Motor neurons stimulate muscle fibers.
  • Calcium ions released, allowing actin and myosin interaction.
  • ATP provides energy for muscle contraction.
• Muscles work in pairs:
  • Agonist (prime mover).
  • Antagonist (opposes the agonist).
  • Synergist (assists the agonist).

Nervous System

• The nervous system controls and coordinates body functions.
• Central nervous system (CNS): Brain and spinal cord.
• Peripheral nervous system (PNS): Nerves outside the CNS.
• Neurons: Nerve cells that transmit electrical signals.
  • Cell body (soma).
  • Dendrites (receive signals).
  • Axon (transmits signals).
  • Synapse (junction between neurons).
• Neurotransmitters: Chemical messengers that transmit signals across synapses.
• Divisions of the PNS:
  • Somatic nervous system: Voluntary control of skeletal muscles.
  • Autonomic nervous system: Involuntary control of smooth muscle, cardiac muscle, and glands.
• Divisions of the autonomic nervous system:
  • Sympathetic nervous system: "Fight or flight" response.
  • Parasympathetic nervous system: "Rest and digest" response.
• Brain regions and functions:
  • Cerebrum: Higher-level functions (thought, memory, language).
  • Cerebellum: Coordination and balance.
  • Brainstem: Basic life functions (breathing, heart rate).

Endocrine System

• The endocrine system regulates body functions through hormones.
• Glands: Secrete hormones into the bloodstream.
• Major endocrine glands:
  • Pituitary gland: Master gland controlling other glands.
  • Thyroid gland: Regulates metabolism.
  • Adrenal glands: Produce hormones for stress response.
  • Pancreas: Regulates blood sugar.
  • Ovaries (female): Produce estrogen and progesterone.
  • Testes (male): Produce testosterone.
• Hormones: Chemical messengers that travel through the bloodstream to target cells.

Cardiovascular System

• Transports oxygen, nutrients, hormones, and waste products throughout the body.
• Heart: Pumps blood.
  • Chambers: Atria (receive blood) and ventricles (pump blood).
  • Valves: Prevent backflow of blood.
  • Blood vessels:
    • Arteries: Carry blood away from the heart.
    • Veins: Carry blood toward the heart.
    • Capillaries: Site of exchange between blood and tissues.
• Blood:
  • Red blood cells (erythrocytes): Carry oxygen.
  • White blood cells (leukocytes): Immune defense.
  • Platelets (thrombocytes): Blood clotting.
  • Plasma: Liquid portion of blood.
• Blood circulation:
  • Pulmonary circulation: Heart to lungs and back.
  • Systemic circulation: Heart to body and back.

Respiratory System

• Facilitates gas exchange between the body and the environment.
• Lungs: Site of gas exchange.
  • Airways:
    • Nose/mouth.
    • Pharynx.
    • Larynx.
    • Trachea.
    • Bronchi.
    • Bronchioles.
    • Alveoli (air sacs).
• Breathing mechanism:
  • Inhalation: Diaphragm contracts, increasing chest volume.
  • Exhalation: Diaphragm relaxes, decreasing chest volume.
• Gas exchange:
  • Oxygen diffuses from alveoli into blood.
  • Carbon dioxide diffuses from blood into alveoli.

Digestive System

• Breaks down food into smaller molecules for absorption.
• Organs:
  • Mouth: Mechanical and chemical digestion begins.
  • Esophagus: Transports food to stomach.
  • Stomach: Churns food and mixes with gastric juices.
  • Small intestine: Major site of nutrient absorption.
  • Large intestine: Absorbs water and forms feces.
  • Liver: Produces bile.
  • Gallbladder: Stores bile.
  • Pancreas: Produces digestive enzymes.
• Digestion process:
  • Mechanical digestion: Chewing, churning.
  • Chemical digestion: Enzymes break down food molecules.
• Absorption: Nutrients pass from the small intestine into the bloodstream.
• Elimination: Waste products are eliminated as feces.

Urinary System

• Filters blood and eliminates waste products as urine.
• Kidneys: Filter blood and produce urine.
• Ureters: Transport urine from kidneys to bladder.
• Bladder: Stores urine.
• Urethra: Transports urine from bladder to outside the body.
• Nephron: Functional unit of the kidney.
  • Filtration: Water and small molecules pass from blood into nephron.
  • Reabsorption: Useful substances are returned to the blood.
  • Secretion: Waste products are actively transported into the nephron.

Reproductive System

• Enables reproduction.
• Male reproductive system:
  • Testes: Produce sperm and testosterone.
  • Ducts: Transport sperm.
  • Glands: Produce seminal fluid.
  • Penis: Delivers sperm to female reproductive tract.
• Female reproductive system:
  • Ovaries: Produce eggs and estrogen/progesterone.
  • Fallopian tubes: Transport eggs to uterus.
  • Uterus: Site of fetal development.
  • Vagina: Receives sperm and serves as birth canal.