Human Body Structure - Quick Reference

Terms to Know

  • Anatomy: study of the form and structure of an organism
  • Physiology: study of the processes of living organisms, or why and how they work
  • Pathophysiology: study of how disease occurs and the responses of living organisms to disease processes
  • Histology: study of tissues
  • Cytology: study of cells
  • Homeostasis: ability to maintain relatively stable internal conditions; dynamic state of equilibrium or balance

Structural Organization

  • Atoms → Molecules → Protoplasm → Organelles → Cells → Tissues → Organs → Organ Systems → Organism

Protoplasm

  • Basic structure of all life
  • Composed of elements such as carbon, oxygen, hydrogen, sulfur, nitrogen, and phosphorus
  • Life cannot be created by simply combining these elements

Cells

  • Simplest unit of living matter that can maintain life and reproduce; basic building block of life
  • Protoplasm forms this basic unit
  • Microscopic structures that carry on all functions of life
  • Functions: taking in food and oxygen; produce heat and energy; move and adapt to their environment; eliminate wastes; perform special functions; and reproduce to create new identical cells
  • The human body contains trillions of cells
  • Cells vary in shape and size and perform many different functions

Prokaryotes vs Eukaryotes

  • Two categories: Prokaryotes and Eukaryotes

Prokaryotes

  • Single cell organism
  • Kingdom Monera
  • Lacks a cell nucleus
  • Internal structure is less organized than in other cells
  • Genetic information is contained within the cell
  • Two most common: blue-green bacteria and true bacteria

Blue-green bacteria

  • Ability to produce their own food like plants
  • Most bacteria obtain food from other sources
  • Less complex than eukaryotes
  • Still have basic internal characteristics (cytoplasm, chromosomal material, cell membrane and wall, ribosomes; some have flagellum for mobility)

Eukaryotes

  • Organism made up of cells that have a nucleus
  • May be single-celled (Kingdom Protista) or billions of cells (plant and animal kingdoms)
  • Single-celled eukaryotes include paramecia, euglena, and diatoms
  • Human body has at least 85 different cell types
  • All eukaryotes have organelles
  • Organelles: smaller parts of the cell with specific functions

Organelles

  • Cell structures that help a cell to function
  • Located in cytoplasm
  • Main organelles: Nucleus, Nucleolus, Chromatin Network, Centrosome, Mitochondria, Ribosomes, Endoplasmic Reticulum, Lysosomes, Golgi Apparatus, Vesicle, Vacuole

Nucleus

  • "Brain" of the cell
  • Largest and most identifiable part
  • Controls many cell activities, including reproduction
  • Important in cell division
  • Site of much biotechnology manipulation
  • Round or oval in structure; typically found in the middle of the cell
  • Surrounded by a membrane that controls passage of materials in and out of the area
  • Contains DNA (located on chromosomes)

Genes & DNA

  • Genes: Regions within the chromosome; each chromosome has several thousand genes that determine hereditary characteristics
  • DNA (deoxyribonucleic acid): comprise each gene; genetic material that regulates the activities of the cell

Diploidy and Chromosome Numbers

  • Most organisms are diploid — two chromosomes for each trait
  • Humans: 23 pairs
  • Goldfish: 90 chromosomes, 45 pairs

Nucleolus

  • Located in cell nucleus
  • Important in reproduction (RNA)

Chromatin Network

  • Located in nucleus
  • Forms chromosomes which contain genes that carry inherited characteristics; DNA bases: A-T and G-C
  • Males: XY; Females: XX

Centrosome

  • Located in cytoplasm near the nucleus
  • Contains 2 centrioles important in reproduction

Mitochondria

  • Located throughout the cytoplasm
  • "Powerhouse" of the cell
  • Helps produce energy (chemical energy carriers: ATP to ADP); converts food into usable energy
  • Contains DNA
  • Can replicate themselves
  • Rod-shaped

Ribosomes

  • Protein synthesis
  • Make proteins for cellular use and communication
  • May be attached to endoplasmic reticulum

Endoplasmic Reticulum

  • Transport system of channels
  • Makes and transports proteins
  • Layered membranous
  • Smooth Endoplasmic Reticulum: does not contain ribosomes; assists in cholesterol synthesis, fat metabolism, and detoxification of drugs
  • Rough Endoplasmic Reticulum: protein synthesis

Lysosomes

  • Sacks of digestive enzymes
  • Store enzymes that break down food into chemical compounds
  • Destroy cell organelles and the cell itself

Golgi Apparatus

  • Synthesizes carbohydrates (CHO) and transports enzymes/hormones; packing of materials
  • Also called Golgi bodies
  • Looks like a thick elastic band folded several times
  • Adds modifications to unfinished proteins
  • Make lysosomes

Vesicle

  • Fluid-filled sack

Vacuole

  • Containers
  • Large organelle, without specific shape
  • Store waste or raw materials used in synthesis of proteins

Cellular Processes

  • Respiration
  • Osmosis
  • Diffusion
  • Photosynthesis

Respiration

  • Cells break down carbohydrates and other molecules to produce energy
  • Oxidation of glucose is a common form of respiration
  • Breaks sugar into water, carbon dioxide, and energy
  • Energy is used to do the work of the cell

Osmosis & Diffusion

  • Transport of raw materials, wastes, and synthesized materials out of the cell
  • Diffusion: movement of molecules from areas of high concentration to low concentration
  • Osmosis: movement of water through a membrane from areas of high concentration to areas of low concentration
  • Diffusion and osmosis help the cell reach equilibrium

Cellular Reproduction

  • Fission
  • Mitosis
  • Meiosis

Fission

  • Prokaryotes
  • Cell grows larger and makes a second copy of its DNA
  • Cell membrane divides the cell by growth of a transverse septum
  • Two new cells form as division grows inward from either side
  • Result: two cells called daughter cells; also known as binary fission

Mitosis

  • Form of asexual reproduction where a cell divides into 2 identical cells
  • Eukaryotes
  • Replaces dead or injured cells
  • Some cells do not reproduce after birth (e.g., nerve and muscle cells)
  • Requires 6 stages: Interphase, Prophase, Metaphase, Anaphase, Telophase, Cytokinesis
  • Produces cells identical to the original cell
  • Have the entire complement of chromosomes existing in pairs — diploid

Meiosis

  • Sex cells (gametes) divide by this process
  • Female cells (ova) and male cells (sperm)
  • Uses 2 separate cell divisions to produce 4 new cells

Meiosis (continued)

  • During meiosis the number of chromosomes is reduced to 23, or 1/2 the number found in cells created by mitosis
  • Sperm + ovum → zygote (46 chromosomes)
  • Normal body cells: 46; sex cells: 23

Meiosis Stages

  • Meiosis I: Interphase I, Prophase I, Metaphase I, Anaphase I, Telophase I, Cytokinesis I
  • Meiosis II: Interphase II, Prophase II, Metaphase II, Anaphase II, Telophase II, Cytokinesis II

Tissue

  • Although most cells contain the same basic parts, they vary greatly in shape, size, and special function

  • When cells of the same type join together for a common purpose, they form a tissue

  • Tissues are 60-99% water with tissue fluid

  • Tissue is slightly salty in nature and is called tissue fluid

  • If there is an insufficient amount of tissue fluid, dehydration occurs

  • If there is an excess amount of tissue fluid, edema (swelling) occurs

4 Main Groups of Tissues

  • Epithelial tissue – secrete and protect
  • Connective tissue – support and connect
  • Nerve tissue – control and communicate
  • Muscle tissue – move and protect

Epithelial Tissue

  • Main tissue in the skin; covers the surface of the body
  • Forms lining of intestinal, respiratory, circulatory, and urinary tracts, as well as body cavities
  • Forms body glands to produce secretions for the body

Connective Tissue

  • Soft and hard classes; also liquid connective tissue
  • Soft: Adipose (fat storage, insulation, padding) and Fibrous connective tissues (ligaments and tendons)
  • Hard: Cartilage and bone
  • Cartilage: between bones, shock absorber, provides flexibility; found in nose, ears, larynx
  • Bone (osseous tissue): rigid framework; contains calcium salts, nerves, and blood vessels
  • Blood and lymph are liquid connective tissues
  • Blood carries nutrients and oxygen; lymph transports tissue fluid, proteins, fats, and other materials

Nerve Tissue

  • Made of neurons; transmits impulses
  • Nerves, brain, and spinal cord are composed of nerve tissue

Muscle Tissue

  • Produces power and movement by contraction
  • Highly cellular, well vascularized
  • 3 types: Skeletal, Cardiac, Visceral (smooth)

Membranes

  • Combination of epithelial and connective tissues
  • Mucous, Serous, Synovial, Dense fibrous, Cutaneous

Mucous

  • Lines body cavities; moist membrane; absorption and secretion

Serous

  • Lines closed body cavities and secretes serous fluid to reduce friction (e.g., pleura, peritoneum, pericardium)

Synovial

  • Tough, fibrous tissue that lines the cavities of freely movable joints

Dense fibrous

  • Tough, opaque protection (dura mater, periosteum, sclera)

Cutaneous

  • Dry membrane (skin)

Organ

  • Group of different tissues that work together for a special function
  • Examples: Heart, Stomach, Lungs, Skin

Organ System

  • Organs and other parts join for a particular function
  • Integumentary, Skeletal, Muscular, Nervous, Endocrine, Cardiovascular, Lymphatic/Immune, Respiratory, Digestive, Urinary, Reproductive