Histology study guide

• What is histology?
  The study of tissues, their structures, and how they are arranged to form organs.

• What are the four main types of tissues in the body?

  1. Epithelial

  2. Connective

  3. Muscle

  4. Nervous

Connective Tissue

• General characteristics:

  • Most abundant and widely distributed tissue type

  • Provides support, protection, and binding

  • Vascularity varies (cartilage = avascular, bone = highly vascular)

• Main components:

  1. Cells – specialized for tissue type

  2. Fibers – provide support/strength

  3. Ground substance – fills space between cells & fibers

• Difference between ground substance and fibers:

  • Ground substance: gel-like material that supports cells & allows diffusion

  • Fibers: structural proteins that provide strength & flexibility

• Three main types of connective tissue fibers:

  1. Collagen fibers – strong, resist pulling forces

  2. Elastic fibers – stretch and recoil

  3. Reticular fibers – form supportive networks

• Types of cells in connective tissue:

  • Fibroblasts (make fibers/ground substance)

  • Macrophages (defense)

  • Mast cells (inflammation, histamine release)

  • Adipocytes (fat storage)

  • Chondrocytes (cartilage)

  • Osteocytes (bone)

  • Blood cells

• Types, locations, and functions:

  • Loose connective tissue:

    • Areolar → under epithelium, cushions organs

    • Adipose → under skin, around organs, stores energy & insulates

    • Reticular → lymph nodes, spleen, supports immune cells

  • Dense connective tissue:

    • Regular → tendons, ligaments (parallel collagen for strength)

    • Irregular → dermis of skin (random collagen for multidirectional strength)

    • Elastic → walls of arteries, allows stretch/recoil

  • Cartilage:

    • Hyaline → nose, trachea, embryonic skeleton, smooth surfaces at joints

    • Elastic → external ear, epiglottis, flexible support

    • Fibrocartilage → intervertebral discs, pubic symphysis, shock absorption

  • Bone: rigid support, protection, stores calcium, blood cell production

  • Blood: transport of gases, nutrients, wastes, immunity

Epithelial Tissue

• General characteristics:

  • Covers body surfaces & lines cavities

  • Forms glands

  • Cells tightly packed, little extracellular material

  • Avascular (gets nutrients via diffusion)

  • High regeneration rate

• Role of the basement membrane:

  • Anchors epithelium to connective tissue

  • Provides support and selective filtration

• Simple vs. stratified:

  • Simple: single cell layer → absorption, secretion, filtration

  • Stratified: multiple layers → protection

• Cell shape differences:

  • Squamous: flat, scale-like

  • Cuboidal: cube-shaped

  • Columnar: tall, column-shaped

• Types, locations, functions:

  • Simple squamous: lungs (alveoli), lining of blood vessels → diffusion

  • Simple cuboidal: kidney tubules, glands → secretion, absorption

  • Simple columnar: digestive tract → absorption, secretion (may have microvilli or cilia)

  • Stratified squamous: skin, mouth, esophagus → protection

  • Stratified cuboidal: sweat glands, salivary glands → secretion

  • Stratified columnar: rare, male urethra → protection, secretion

  • Pseudostratified columnar: respiratory tract → secretion, movement of mucus (cilia)

  • Transitional: bladder → stretches to allow filling

Muscle Tissue

• Relation to movement:

  • Contracts to produce movement of body and materials inside body

• Three types:

  1. Skeletal (striated):

     • Attached to bones

     • Voluntary movement, posture, heat production

  2. Smooth (visceral):

     • Walls of hollow organs (stomach, intestines, blood vessels)

     • Involuntary, moves substances through body

  3. Cardiac:

     • Heart wall

     • Involuntary, pumps blood, has intercalated discs

• Voluntary vs. involuntary:

  • Skeletal = voluntary

  • Smooth & cardiac = involuntary

Nervous Tissue

• General characteristics:

  • Specialized for communication via electrical impulses

  • Coordinates body functions

• What is a neuron?
  The functional cell of nervous tissue that transmits signals.

• Major parts of a neuron:

  • Cell body (soma): contains nucleus, controls cell

  • Dendrites: receive signals

  • Axon: sends signals away

• Location & function:

  • Found in brain, spinal cord, and nerves

  • Functions: sensation, integration, motor control, regulation of body activities