Histology


Structure

Function

Location

Simple Squamous Epithelum


  • single layer

  • thin, flat cells

  • nucleus bulges at center

  • thinnest barrier

  • rapid diffusion & filtration

  • secretion in serous membranes

  • air sacs in lungs

  • lining of lumen blood vessels & lymph vessels

  • serous membranes of body cavities 

Simple Cuboidal Epithelium


  • as tall as wide

  • spherical central nucleus

  • absorption & secretion

  • kidney tubules

  • secretory regions

  • ducts of most glands

  • surface of ovary

Simple Columnar Epithelium

Nonciliated


  • taller than wide

  • oval nucleus

  • may contain goblet cells (make mucus)

  • may have microvilli

  • secretion & absorption

  • secretion of mucus

  • inner lining of most digestive track

Ciliated


  • have cilia

  • may contain goblet cells

  • secretion of mucus along apical surface

  • oocyte movement through uterine tube

  • lining of larger bronchioles (air passageways) of lung and uterine tubes

Keratinized Stratified Squamous Epithelium


  • Multiple cell layers

  • Basal cells cuboidal/polyhedral

  • Apical cells squamous, dead, filled w/ keratin

  • Protect underlying tissues from abrasion

  • Epidermis of skin

Non-Keratinized Stratified Squamous Epithelium


  • Multiple layers, basal cells cuboidal 

  • apical squamous

  • Cells lack keratin

  • Protect underlying tissue from abrasion

  • Oral cavity

  • Esophagus

  • Lining vagina & anus

Stratified Cuboidal


  • 2+ layers

  • Cells are as tall as wide

  • Protect and secrete

  • Ducts of complex glands

  • Exocrine -> ovarian follicles



Cell building & Aging:

> normal continuous process with body signs

> not so obvious on a molecular level

Cell Death: 

> cell death by 2 mechanisms

  • Killed by harmful agents or mechanical damage

  • Induced to commit suicide

    • Apoptosis

Apopstosis:

  1. Destruction of DNA polymerase

  2. Digest DNA

  3. Digest cytoskeleton

  4. Condensation of cytosol & destruction of organelles

  5. Formation of blebs (bubbles)

  6. Initiation of other signals to stimulate destruction

> occurs to promote proper development and remove harmful cells

Clinical View - Tumors:

> Regulatory Mechanisms

  • Signal cells to divide or stop

> Cell Signaling Disrupted

  • Tumors arise

  • Interferes with function of normal surrounding cells

  • May enter blood or lymph & metastasize 

    • Metastasize: for cancer to spread from the place it started to other parts of the body



Glands:

> individual cells or multicellular organs composed of epithelial

> endocrine or exocrine

  • Exocrine: secretes onto surface of body

> Endocrine:

  • Lack ducts

  • Secretes hormones into blood

> Exocrine:

  • Invaginated epithelium in connective tissue

  • Connoted with epithelial surface by duct

    • Sweat glands, mammary glands, salivary glands

> Unicellular Exocrine:

  • Do not contain ducts

  • Close to epithelial surface

  • Most common is goblet cell

> Multicellular Exocrine:

  • Numerous cells

  • Acini: cell clusters that produce secretion (leaf)

  • Ducts: transport secretions to epithelial surface (branch)

  • Surrounded by fibrous capsule

> Classification of Glands:

  • Simple Glands - a single on branched duct

    • Simple tubular, simple branched tubular, simple coiled tubular, simple acinar, simple branched acinar

      • Close to surface

  • Compound Glands - branched ducts

    • Compound tubular, compound acinar, compound tubular acinar

      • Deep

  • Tubular looks like a tube

  • Acinar is rounder

> Functions Secretion:

  • Merocrine Glands

    • Secrete toward the surface

    • Small vesicles

  • Apocrine Glands

    • Pinching toward surface, bubbling

    • Breast feeding

  • Holocrine Gland

    • Cells dividing pushing up

    • Disintegrating cells becoming the secretion






Structure

Function

Location

Areolar CT


  • Viscous ground substance

  • Few collagen & elastic fibers

  • Thick liquid shell

  • Binds

  • “glue”


Adipose CT


  • Closely packed adipocytes

  • Nucleus pushed to edge of cell

  • Store energy

  • Cushions & protects


Reticular CT


  • Viscous ground substance

  • Meshwork of reticular fibers

  • Provides stroma to lymphatic organs


Dense Regular CT


  • Parallel arrays of collagen fibers

  • fibroblasts

  • Make up ligaments and tendons

  • Scarce ground substance

  • Very strong


Dense Irregular CT


  • Collagen fibers randomly arranged and clumped together

  • Fibroblasts in spaces among fibers

  • Looks marbled

  • Strength & resists stress


Hyaline Cartilage


  • Glassy-appearing matrix

  • Irregularly arranged chondrocytes

  • Absorb shock in the body


Elastic Cartilage


  • Abundant elastic fibers that form web-like mesh

  • Chondrocytes packed closely

  • Maintains shake while providing flexibility

  • External ear

Fibrocartilage


  • Readily visible

  • Parallel collagen 

  • chondrocytes

  • Resists compression

  • Shock absorber in joint







Structure

Function

Location

Bone


  • Very solid

  • Looks very white/yellow

  • Spongy is more course

  • Support & protect


Blood/Lymph


  • Contains formed elements

  • Dissolved protein w/in liquid ground substance

  • Leukocytes help protect the body from infections

  • Platelets help with preventing blood clotting




Functions of Connective Tissue:

  • Physical protection

  • Support & structural framework

  • Binds structures

  • Storage

  • Transport

  • Immune protection



3 Things Needed for CT:

  1. Fiber

    1. Elastic

      1. Long & slender, stretch & recoil

    2. Collagen

      1. Thick & strong

    3. Reticular 

      1. Smaller, not as strong

  2. Cells

    1. Resident

      1. Have a home

    2. Wondering 

      1. No home

  3. Ground Substance

    1. Fluid part

    2. Solid  & semi solid

    3. Changes based on cells



Clinical View: Scurvy

> caused by vitamin C deficiency (need for fibers)

> Symptoms: weals, gum ulceration, hemorrhages, abnormal bone growth

> caused by nutritional deficiencies

> eat more vitamin C




Structure

Function

Location

Muscle Tissue


  • Cells contract when stimulated

  • Voluntary = somatic

  • Involuntary = visceral


Skeletal Muscle Tissue


  • Long, cylindrical cells arranged parallel & unbranched

  • Fibers are multinucleated

  • Visible striations

  • Fiber is under voluntary control

  • Movement

  • Temperature regulation

  • Attaches to bones

  • Sometimes attaches to skin

  • Forms external urethral and anal sphincters

Cardiac Muscle Tissue


  • Medium-sized

  • Branching cells

  • 1-2 centrally located nuclei

  • Intercalated discs between cells

  • Involuntary control

  • Visible striations

  • Pumps blood through heart and blood vessels


  • Heart wall

Smooth Muscle Tissue


  • Cells are short and fusiform

  • One centrally located nucleus

  • No visible striations

  • Involuntary controls

  • Moves & propels materials through internal organs

  • Controls the size of the lumen

  • Walls of hollow internal organs

  • Intestines, stomach, airways, bladder, uterus

  • Iris of the eye





Structure

Function

Location

Nervous Tissue


  • Contains neurons

  • Cell body, dendrites, axon

  • Glial cells (lack processes)

  • Receive, process, & transmit nerve impulses

  • Glial Cells: protect, nourish, & support neurons

  • Brain, spinal cord, and nerves






Roles of Tissues in an Organ:


1. Mucosa

> directly faces the hollow space of the organ (Lumen)

> “what touches the stuff inside”

> 3 components:

  1. Epithelium -> actual lining

  2. Areolar connective tissue -> supports the epithelium

  3. Smooth muscle -> allows mucosa to move/fold

> lining + support + local movement



2. Submucosa

> the support layer

> plumbing + wiring + support

> can contain

  • Blood vessels

  • Glands

  • Nerves



3. Muscularis

> mostly smooth muscle

> movement

> Oblique, Circular, Longitudinal



4. Adventita v. Serosa

> Serosa = slippery

> Adventitia = attaches

> they are alternatives



Body Membranes:

  • Tissue that covers or lines body cavity

    • Mucous

    • Serous

    • Cutaneous

    • Synovial




Tissue Development:

> Ectoderm = outside

  • Outside & nervous system

> Mesoderm - middle

  • Support & movement tissues

> Endoderm = inside

  • Epithelial lining of internal tracts



Tissue Modification:

> Changes in Size/Number

  • Atrophy = smaller (size)

  • Hypertrophy = bigger (size)

  • Hyperplasia = more (#)

> Changes in Type/Organization

  • Metaplasia = different type

  • Dysplasia = abnormal

  • Neoplasia  = uncontrolled growth (tumor)



Neocrosis:

> death of cells or tissues due to injury

> ex. Gangrene




Aging of Tissues:

> support maintenance, replacement of cells & extracellular matrix

> structure & chemical composition of many tissues altered

  • epithelia thins

  • CT loses pliability & resiliency

  • collagen declines

  • bones become brittle

  • muscles atrophy