KAAP 309 Histology: Tissue Types & Classifications - Comprehensive Study Notes

Embryonic Tissues

• Germ layers and adult derivatives

  • Ectoderm: gives rise to epidermis and nervous system

  • Mesoderm: becomes mesenchyme, which eventually differentiates into cardiac muscle, bone, blood, and other connective tissues

  • Endoderm: gives rise to mucous membranes of digestive and respiratory tracts and digestive glands

• Three embryonic tissues and their adult derivatives

  • Three germ layers (germ-tissues) give rise to all adult tissues

  • Ectoderm → epidermis; nervous system

  • Mesoderm → mesenchyme → cardiac muscle, bone, blood, and other connective tissues

  • Endoderm → mucous membranes of digestive/respiratory tracts and digestive glands

Four Primary Tissues

• Epithelial

• Connective

• Muscle

• Nervous

Epithelial Tissue

• Key functions (What does it do?):

  • Protection

  • Absorption

  • Filtration

  • Excretion

  • Secretion

  • Sensory

• Key characteristics:

  • Epithelium

  • Apical surface: borders open space

  • Basal surface: next to underlying connective tissue

  • Microvilli

  • Actin filaments

  • Terminal web

• Naming Epithelial Tissue

  • Shape: Squamous, Cuboidal, Columnar

  • Number of layers: Simple, Stratified

• Simple Epithelium

  • Simple Squamous

  • F: easy diffusion

  • L: lungs, kidneys, vessels

  • Simple Cuboidal

  • F: secretion & absorption

  • L: kidneys, glands, liver

  • Simple Columnar

  • F: secretion & absorption

  • L: GI tract, gallbladder, uterus

• Pseudostratified Columnar Epithelium (Pseudostratified)

  • F: secretion, propulsion of mucus

  • L: trachea and upper respiratory tract; sperm-carrying ducts and large glands

• Stratified Epithelium

  • Stratified Squamous Epithelium

  • F: protection

  • L: esophagus, mouth, vagina; skin (keratinized)

  • Stratified Squamous Epithelium (structure notes)

  • Nuclei, Basement membrane; may include dead squamous cells in keratinized skin

  • Stratified Cuboidal Epithelium

  • F: secretion

  • L: sweat glands, ovaries, testes

  • Transitional Epithelium

  • F: stretches

  • L: urinary tract and bladder

• Additional notes on stratified squamous epithelium

  • Layered arrangement with living epithelial cells resting on connective tissue; in some areas, dead cells (keratinized) are present in skin

• Transitional epithelium visuals

  • Epithelium can stretch and unfold as the lumen changes size (bladder examples)

• Glandular Epithelia (overview)

  • All glands produce a product (secretion)

  • Classified by:

  • Where they secrete: Endocrine (inside) vs Exocrine (outside)

  • Number of cells: Unicellular vs multicellular

  • Secretory product: Serous or Mucous

• Exocrine Glands (Structure Classification)

  • Simple coiled tubular gland (example: Sweat gland)

  • Compound acinar gland (example: Mammary gland)

  • Compound tubuloacinar (example: Pancreas)

• Exocrine Glands (Secretion Styles)

  • Examples: Pancreas, sweat glands, salivary glands

  • Sebaceous (oil) glands of the skin

  • Mammary glands, sweat glands (axilla)

Connective Tissue

• Major functions

  • Binding & Support

  • Protection

  • Insulating

  • Storing

  • Transportation

• Key characteristics

  • Extracellular matrix > cells

  • Common origin

• Connective tissue types (11 total)

  • Loose Areolar

  • F: support, defense, storage

  • L: universal; present in all mucous membranes as lamina propria

  • Adipose (Fat)

  • F: support, defense, insulation, storage

  • L: universal; ~ 18% of body weight

  • Loose Reticular Connective Tissue

  • F: support defense cells

  • L: lymphoid organs (lymph nodes, bone marrow, spleen)

  • Dense Regular Connective Tissue

  • F: strength

  • Components: collagen fibers, ground substance, fibroblast nuclei

  • L: tendons, ligaments, aponeuroses

  • Dense Irregular Connective Tissue

  • F: durability; withstand stress from multiple directions

  • L: capsules, dermis, digestive tract, sheath around cartilage/bone

  • Dense Elastic Connective Tissue

  • F: recoil

  • L: arteries, some spinal ligaments, vocal cords

  • Hyaline Cartilage

  • F: support & cushion

  • L: ends of bones, costal cartilages, nose, trachea, and larynx; most of the fetal skeleton

  • Elastic Cartilage

  • F: shape and flexibility

  • L: external ear; epiglottis

  • Fibrocartilage

  • F: strength and shock absorption

  • L: intervertebral discs, menisci, pubic symphysis

  • Bone

  • Description: hard, calcified matrix (osteons) with peripheral osteocytes; tree ring pattern

  • F: support and protection

  • L: bone

  • Blood

  • Description: cells (erythrocytes) suspended in plasma

  • F: transport nutrients, wastes, respiratory gases, and other substances

• Connective Tissue (histology) – What it does

  • Binding & Support; Protection; Insulating; Storing; Transportation

• Bone, Blood, and other connective tissues are part of the connective tissue proper or specialized connective tissues

Muscle Tissue

• What does it do? Contraction/Movement

• Types: Skeletal, Smooth, Cardiac

• Skeletal Muscle

  • Structure: long, cylindrical fibers with many peripheral nuclei; patterned striations

  • Location: attached to skeleton (skeletal muscles)

• Smooth Muscle

  • Structure: spindle-shaped cells with one central nucleus; no visible striations

  • Location: digestive system, urinary tract/bladder, uterus, blood vessels

• Cardiac Muscle

  • Structure: branching cells with one central nucleus; intercalated discs

  • Location: heart

Nervous Tissue

• What it does: responds to stimuli; generates and transmits electrical impulses

• Key characteristics

  • Neuron processes: axon, dendrites; cell body

  • Nuclei of supporting cells (neuroglia)

• Neurons vs Neuroglia

  • Neurons: highly specialized nerve cells that generate and transmit impulses

  • Neuroglia: support, insulate, and protect neurons

Glands & Membranes

• Glandular epithelia

  • All glands produce a product (secretion)

  • Classified by secretion site: Endocrine (inside) vs Exocrine (outside)

  • Classified by number of cells: unicellular vs multicellular

  • Secretions can be serous or mucous

• Exocrine glands (structure/classification)

  • Simple coiled tubular gland (sweat gland)

  • Compound acinar gland (mammary gland)

  • Compound tubuloacinar (pancreas)

• Exocrine glands (secretion styles)

  • Examples: pancreas, sweat glands, salivary glands

  • Sebaceous (oil) glands of the skin

  • Mammary glands, sweat glands (axilla)

• Cutaneous membranes (skin)

  • Keratinized stratified squamous epithelium (epidermis) attached to connective tissue (dermis)

  • Dry membrane

  • The cutaneous membrane is the skin that covers the body surface

• Mucous membranes

  • Stratified squamous or simple columnar epithelium over a layer of areolar connective tissue (lamina propria)

  • Line all body cavities that open to the outside world: Digestive, Respiratory, Urinary, Reproductive

  • Wet membrane

• Serous membranes

  • Simple squamous (mesothelium) over a thin layer of areolar connective tissue

  • Line all body cavities that do NOT open to the outside world: Pleurae, Pericardium, Peritoneum

  • Wet membrane