Human Body: Organs, Systems, and Structure

Key Questions

• Chemical composition of the human body?
• Four main types of tissue in the human body?
• Nine major organ systems in the human body?

Overview

• The human body consists of living cells, extracellular materials, tissues, organs, and systems.
• Related topics: anatomy, physiology, blood, cardiovascular system, digestive system, endocrine system, renal system, skin, muscle system, nervous system, reproductive system, respiration, sensory reception, skeletal system, aging, growth, prenatal development, human development.

Chemical Composition

• Water: 60% of body weight, found in blood plasma, lymph, and interstitial fluid.
• Organic Compounds: Lipids, proteins, carbohydrates, nucleic acids.
  • Lipids: Fats (energy reserve), phospholipids, cholesterol (cell membranes).
  • Proteins: Structural (cell membrane, hair, nails, collagen), functional (enzymes).
  • Carbohydrates: Fuels (sugars, glycogen).
  • Nucleic Acids: DNA (genetic information), RNA (carries out DNA instructions).
• Inorganic Minerals: Calcium, phosphorus, sodium, magnesium, iron (various roles in metabolic processes).

Organization of the Body

• Cell: Basic living unit, capable of growth, metabolism, response to stimuli, reproduction.
• Tissues: Four basic types:
  1. Epithelial: Covers body surfaces, lines organs and cavities.
  2. Muscle: Capable of contraction, forms musculature.
  3. Nerve: Conducts electrical impulses, forms nervous system.
  4. Connective: Binds body structures, includes bone and blood as specialized types.
• Organs: Groups of tissues forming structural and functional units (e.g., heart).
• Nine Major Organ Systems:
  1. Integumentary System: Skin and associated structures; protects body.
  2. Musculoskeletal System: Muscles and bones; moves body and protects organs.
  3. Respiratory System: Breathing passages, lungs; obtains oxygen, expels carbon dioxide.
  4. Circulatory System: Heart, blood, vessels; circulates oxygen, nutrients, and waste.
  5. Digestive System: Mouth to intestines; breaks down food, absorbs nutrients, eliminates waste.
  6. Nervous System: Sensory organs, brain, spinal cord, nerves; processes information, controls responses.
  7. Endocrine System: Hormone-secreting glands; coordinates body processes.
  8. Reproductive System: Sex organs; enables reproduction and species continuation.

Human Body in Vertebrates

• Humans are part of the order Primates, subphylum Vertebrata, phylum Chordata.
• Bilateral symmetry, dorsal supporting rod (notochord replaced by vertebral column), gill slits (lost in adults).
• Vertebrate Characteristics: Internal skeleton, hair, mammary glands, developed sense organs.
• Unique features: Two-legged (bipedal) posture, highly developed brain (neocortex).