JC

Chapter 5: Tissues - Comprehensive Study Notes

Intercellular Junctions

  • Tight junctions

    • Close space between cells by fusing cell membranes

    • Example: cells that line the small intestine

    • Significance: create a barrier to paracellular diffusion and help maintain distinct membrane domains

  • Desmosomes

    • Bind cells by forming “spot welds” between cell membranes

    • Example: cells of the outer skin layer

    • Significance: resist shearing forces and provide mechanical integrity to tissues with stress

  • Gap junctions

    • Form tubular channels between cells that allow exchange of substances

    • Example: muscle cells of the heart and digestive tract

    • Significance: enable direct intercellular communication and coordination (electrical/metabolic coupling)

Four Major Tissue Types

  • Epithelial

    • Function: protection, secretion, absorption, excretion

    • Location: cover body surface, cover and line internal organs, compose glands

    • Distinguishing characteristics: lacks blood vessels; cells readily divide; cells tightly packed

  • Connective

    • Function: bind, support, protect, fill spaces, store fat, produce blood cells

    • Location: widely distributed throughout the body

    • Distinguishing characteristics: good blood supply; cells farther apart than epithelial cells; extracellular matrix in between

  • Muscle

    • Function: movement

    • Location: attached to bones, in the walls of hollow internal organs, heart

    • Distinguishing characteristics: able to contract in response to specific stimuli

  • Nervous

    • Function: conduct impulses for coordination, regulation, integration, and sensory reception

    • Location: brain, spinal cord, nerves

    • Distinguishing characteristics: cells communicate with each other and other body parts

Epithelial Tissues

  • Simple Squamous Epithelium

    • Structure: Single layer, flattened cells

    • Function: Filtration, diffusion, osmosis, covers surface

    • Location: Air sacs of lungs; walls of capillaries; linings of blood and lymph vessels; part of membranes lining body cavities and covering viscera

  • Simple Cuboidal Epithelium

    • Structure: Single layer, cube-shaped cells

    • Function: Protection, secretion, absorption

    • Location: Surface of ovaries; linings of kidney tubules; linings of ducts of certain glands

  • Simple Columnar Epithelium

    • Structure: Single layer, elongated (tall) cells

    • Function: Protection, secretion, absorption

    • Location: Linings of uterus, stomach, and intestines

      (Fake/false )

  • Pseudostratified Columnar Epithelium

    • Structure: Single layer, elongated cells; appears stratified due to varying nuclei positions

    • Function: Protection, secretion, movement of mucus and substances

    • Location: Linings of respiratory passages

  • Stratified Squamous Epithelium

    • Structure: Many layers with top cells flattened

    • Function: Protection

    • Location: Superficial portion of skin and linings of oral cavity, vagina, and anal canal

  • Stratified Cuboidal Epithelium

    • Structure: 2 or 3 layers, cube-shaped cells

    • Function: Protection

    • Location: Linings of ducts of mammary glands, sweat glands, salivary glands, and pancreas

  • Stratified Columnar Epithelium

    • Structure: Top layer of elongated cells, lower layers of cube-shaped cells

    • Function: Protection, secretion

    • Location: Part of the male urethra and lining of larger ducts of excretory glands

  • Transitional Epithelium

    • Structure: Many layers of cube-shaped and elongated cells

    • Function: Distensibility, protection

    • Location: Inner lining of urinary bladder and linings of ureters and part of urethra

Glandular Epithelium and Secretion

  • Gland structure categories (epithelial origin):

    • Simple tubular

    • Simple branched tubular

    • Simple coiled tubular

    • Simple branched alveolar (alveolar = acinar)

    • Compound tubular

    • Compound alveolar

    • Compound tubuloalveolar

  • Secretory units

    • Unicellular or multicellular

    • Secretion can be released via different modes

  • Examples

    • Salivary glands, sweat glands, endocrine glands

  • Secretory mechanisms (illustrative, not exhaustive in this excerpt)

    • Merocrine, Apocrine, Holocrine glands (discussed later with diagrams)

Connective Tissue: Components

  • Extracellular matrix (ECM)

    • Collagen fibers (white fibers): thick, threadlike; provide high tensile strength; Hold structures together

    • Elastic fibers (yellow fibers): bundles of microfibrils embedded in elastin; provide elastic quality to stretchable parts

    • Reticular fibers: thin fibers of collagen; form delicate supportive networks within tissues

  • Ground substance

    • Nonfibrous proteins and other molecules; varying amounts of fluid

    • Fills spaces around cells and fibers

  • Cells associated with connective tissue

    • Fibroblasts: widely distributed, large, star-shaped; secrete proteins that become fibers

    • Macrophages: motile; clear foreign particles from tissues by phagocytosis

    • Mast cells: large cells near blood vessels; release substances that may prevent blood clotting (heparin) and promote inflammation (histamine)

“Proper” Connective Tissues

  • Areolar connective tissue

    • Description: Cells in fluid-gel matrix

    • Function: Binds organs

    • Location: Beneath the skin, surrounds organs

  • Adipose connective tissue

    • Description: Cells in fluid-gel matrix

    • Function: Protects, insulates, and stores fat

    • Location: Beneath the skin, around the kidneys, behind the eyeballs, on the surface of the heart

  • Reticular connective tissue

    • Description: Cells in fluid-gel matrix

    • Function: Supports

    • Location: Walls of liver and spleen

  • Dense regular connective tissue

    • Description: Cells in fluid-gel matrix

    • Function: Binds body parts

    • Location: Tendons, ligaments

  • Dense irregular connective tissue

    • Description: Cells in fluid-gel matrix

    • Function: Sustains tissue tension

    • Location: Dermis

  • Elastic connective tissue

    • Description: Cells in fluid-gel matrix

    • Function: Provides elastic quality

    • Location: Connecting parts of the spinal column, in walls of arteries and airways

“Specialized” Connective Tissues

  • Hyaline cartilage

    • Description: Cells in solid-gel matrix

    • Function: Supports, protects, provides framework

    • Location: Ends of bones, nose, and rings in walls of respiratory passages

  • Elastic cartilage

    • Description: Cells in solid-gel matrix

    • Function: Supports, protects, provides flexible framework

    • Location: Framework of external ear and part of larynx

  • Fibrocartilage

    • Description: Cells in solid-gel matrix

    • Function: Supports, protects, absorbs shock

    • Location: Between bony parts of spinal column, parts of pelvic girdle, and knee

  • Bone

    • Description: Cells in solid matrix

    • Function: Supports, protects, provides framework

    • Location: Bones of skeleton, middle ear

  • Blood

    • Description: Cells and platelets in fluid matrix

    • Function: Transports gases, defends against disease, clotting

    • Location: Throughout the body in a closed system of blood vessels and heart chambers

Bone Microstructure (from the diagrammatic page)

  • Bone tissue components

    • Lamella: concentric layers of bone matrix

    • Osteon: structural unit of compact bone

    • Central canal: contains blood vessels and nerves

    • Lacuna: small spaces containing osteocytes

    • Canaliculi: tiny channels that allow cell-to-cell communication and nutrient/wanic exchange between osteocytes

  • Function of bone microstructure: supports, protects, and provides framework

  • Location: Bones of the skeleton; also present in middle ear

Cartilage and Bone Highlights

  • Hyaline cartilage: End regions of bones; nose; tracheal rings

  • Elastic cartilage: External ear and part of larynx

  • Fibrocartilage: Intervertebral discs; knee joints; pelvic girdle

  • Bone: Rigid framework of body; supports and protection; houses bone marrow

Blood and Membranes

  • Blood components: Blood cells and platelets in a fluid matrix; transports gases; defends against disease; clotting

  • Membranes

    • Definition: Membranes are thin sheetlike layers that cover surfaces; most have two layers of tissue - epithelial and connective

    • Serous membranes: cover surfaces that do not open to the outside; outer layer of organs (visceral) and inner lining of cavities (parietal); epithelial layer secretes serous fluid

    • Mucous membranes: lining of organs that open to the outside (digestive, urinary, reproductive, respiratory); goblet cells produce mucus

    • Cutaneous membrane (skin): epidermis (epithelial) and dermis (connective)

    • Synovial membranes: around synovial joints; produces secretes synovial fluid that lubricates the joint

Muscular Tissues

  • Skeletal Muscle Tissue

    • Structure: Long, threadlike cells; striated; many nuclei

    • Function: Voluntary movements of skeletal parts

    • Location: Muscles usually attached to bones

  • Smooth Muscle Tissue

    • Structure: Shorter cells; single, central nucleus

    • Function: Involuntary movements of internal organs

    • Location: Walls of hollow internal organs

  • Cardiac Muscle Tissue

    • Structure: Branched cells, striated; intercalated discs; typically single nucleus

    • Function: Heart movements

    • Location: Heart

Nervous Tissue

  • Neurons (nerve cells)

    • Structure: Cell with cytoplasmic extensions

    • Function: Sensory reception and conduction of electrical impulses

    • Location: Brain, spinal cord, peripheral nerves

Studying Tissues (Histology) – Exam Preparation Tips

  • Anatomy of Tissues (Structure)

    • Describe the tissue's structure and name part(s) of the tissue

    • List places where the tissue is found

    • For lab midterm – identify the tissue and parts from pictures

  • Physiology of Tissues (Function)

    • What functions are performed by the tissue?

    • How does the tissue perform these functions?