Transcript chapter_5 - The Anatomy Academy

Histology
 Study
of Tissues
 Epithelial Tissue
 Connective Tissue
 Nervous and Muscular Tissue
 Intercellular Junctions, Glands and
Membranes
 Tissue Growth, Development, Death and
Repair
1
The Study of Tissues
 200
Different cell types
 Four primary tissue classes


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epithelial tissue
connective tissue
muscular tissue
nervous tissue
 Histology

study of tissues organ formation
 Organ

(microscopic anatomy)
= structure with discrete boundaries
composed of 2 or more tissue types
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Features of Tissue Classes
 Tissue

= similar cells and cell products
arose from same region of embryo
 Differences


between tissue classes
types and functions of cells
characteristics of matrix (extracellular material)
• fibrous proteins
• ground substance



clear gels (ECF, tissue fluid, interstitial fluid, tissue gel)
rubbery or stony in cartilage or bone
space occupied by cells versus matrix
• connective tissue cells are widely separated
• little matrix between epithelial and muscle cells
3
Tissue Techniques and Sectioning
 Preparation



of histological specimens
fixative prevents decay (formalin)
sliced into thin sections 1 or 2 cells thick
mounted on slides and colored with
histological stain
• stains bind to different cellular components
 Sectioning
reduces 3-dimensional
structure to 2-dimensional slice
4
Sectioning Solid Objects

Sectioning a cell
with a centrally
located nucleus
 Some slices
miss the cell
nucleus
 In some the
nucleus is
smaller
5
Sectioning Hollow Structures

Cross section of
blood vessel, gut,
or other tubular
organ.
 Longitudinal
section of a sweat
gland. Notice
what a single slice
could look like.
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Types of Tissue Sections

Longitudinal section

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Cross section


tissue cut along
longest direction of
organ
tissue cut
perpendicular to length
of organ
Oblique section

tissue cut at angle
between cross and
longitudinal section
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Epithelial Tissue

Layers of closely adhering cells
 Flat sheet with upper surface exposed to the
environment or an internal body cavity
 No blood vessels


underlying connective tissue supplies oxygen
Rests on basement membrane


thin layer of collagen and adhesive proteins
anchors epithelium to connective tissue
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Simple Versus Stratified
Epithelia

Simple epithelium


contains one layer of cells
named by shape of cells
• Stratified epithelium
– contains more than one layer
– named by shape of apical cells
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Simple Squamous Epithelium

Single row of flat cells
 Permits diffusion of substances
 Secretes serous fluid
 Alveoli, glomeruli, endothelium, and serosa
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Simple Cuboidal Epithelium
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Single row cube-shaped cells with microvilli
Absorption and secretion, mucus production
Liver, thyroid, mammary and salivary glands,
bronchioles, and kidney tubules
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Simple Columnar Epithelium

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Single row tall, narrow cells
 oval nuclei in basal half of cell
Absorption and secretion; mucus secretion
Lining of GI tract, uterus, kidney and uterine tubes
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Pseudostratified Epithelium


Single row of cells some not reaching free
surface
 nuclei give layer stratified look
Secretes and propels respiratory mucus
13
Stratified Epithelia
 More
than one layer of cells
 Named for shape of surface cells

exception is transitional epithelium
 Deepest
cells on basement membrane
 Variations


keratinized epithelium has surface layer of
dead cells
nonkeratinized epithelium lacks the layer of
dead cells
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Keratinized Stratified Squamous

Multilayered epithelium covered with dead squamous
cells, packed with keratin
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
epidermal layer of skin
Retards water loss and barrier to organisms
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Nonkeratinized Stratified Squamous
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Multilayered surface epithelium forming moist,
slippery layer
 Tongue, oral mucosa, esophagus and vagina
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Stratified Cuboidal Epithelium
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
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Two or more cell layers; surface cells square
Secretes sweat; produces sperm and hormones
Sweat gland ducts; ovarian follicles and seminiferous
tubules
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Transitional Epithelium

Multilayered epithelium surface cells that change
from round to flat when stretched
 allows for filling of urinary tract
 ureter and bladder
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Connective Tissue
 Widely
spaced cells separated by fibers and
ground substance
 Most abundant and variable tissue type
 Functions
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connects organs
gives support and protection (physical and
immune)
stores energy and produces heat
movement and transport of materials
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Cells of Connective Tissue

Fibroblasts produce fibers and ground substance
 Macrophages phagocytize foreign material and
activate immune system

arise from monocytes (WBCs)

Neutrophils wander in search of bacteria
 Plasma cells synthesize antibodies
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Mast cells secrete
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arise from WBCs
heparin inhibits clotting
histamine that dilates blood vessels
Adipocytes store triglycerides
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Fibers of Connective Tissue
 Collagen


tough, stretch resistant, yet flexible
tendons, ligaments and deep layer of the skin
 Reticular

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fibers
thin, collagen fibers coated with glycoprotein
framework in spleen, lymph nodes, marrow
 Elastic
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fibers (white fibers)
fibers (yellow fibers)
thin branching fibers of elastin protein
stretch and recoil like rubberband (elasticity)
skin, lungs and arteries stretch and recoil
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Connective Tissue Ground Substance
 Gelatinous

absorbs compressive forces
 Consists
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material between cells
of 3 classes of large molecules
glycosaminoglycans – chondroitin sulfate
• disaccharides that attract sodium and hold water
• role in regulating water and electrolyte balance

Proteoglycan (bottlebrush-shaped molecule)
• create bonds with cells or extracellular
macromolecules

adhesive glycoproteins
• protein-carbohydrate complexes bind cell membrane
to collagen outside the cells
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Fibrous Connective Tissue Types
 Loose
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
connective tissue
gel-like ground substance between cells
types
• areolar
• reticular
• adipose
 Dense
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
connective tissue
fibers fill spaces between cells
types vary in fiber orientation
• dense regular connective tissue
• dense irregular connective tissue
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Areolar Tissue
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Loose arrangement of fibers and cells in abundant
ground substance
Underlies all epithelia, between muscles,
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passageways for nerves and blood vessels
Reticular Tissue
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
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Loose network of reticular fibers and cells
Forms supportive stroma (framework) for
lymphatic organs
Found in lymph nodes, spleen, thymus and bone
marrow
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Adipose Tissue
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
Empty-looking cells with thin margins; nucleus pressed
against cell membrane
Energy storage, insulation, cushioning
 subcutaneous fat and organ packing
 brown fat (hibernating animals) produces heat
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Dense Regular Connective Tissue
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
Densely, packed, parallel collagen fibers
 compressed fibroblast nuclei
Tendons and ligaments hold bones together and
attach muscles to bones
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Dense Irregular Connective Tissue

Densely packed, randomly arranged, collagen
fibers and few visible cells


withstands stresses applied in different directions
deeper layer of skin; capsules around organs
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Cartilage
 Supportive
connective tissue with rubbery
matrix
 Chondroblasts produce matrix

called chondrocytes once surrounded
 No


blood vessels
diffusion brings nutrients and removes wastes
heals slowly
 Types

of cartilage vary with fiber types
hyaline, fibrocartilage and elastic cartilage
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Hyaline Cartilage


Rubbery matrix; dispersed collagen fibers; clustered
chondrocytes in lacunae
 supports airway, eases joint movements
Ends of bones at movable joints; sternal ends of ribs;
supportive material in larynx, trachea, bronchi and fetal
skeleton
30
Elastic Cartilage

Hyaline cartilage with elastic fibers
 Provides flexible, elastic support

external ear and epiglottis
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Fibrocartilage
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Hyaline cartilage with extensive collagen fibers (never has
perichondrium)
Resists compression and absorbs shock

pubic symphysis, meniscus and intervertebral discs
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Bone
 Spongy
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bone - spongy in appearance
delicate struts of bone
covered by compact bone
found in heads of long bones
 Compact
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bone - solid in appearance
more complex arrangement
cells and matrix surround vertically oriented
blood vessels in long bones
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Bone Tissue (compact bone)

Calcified matrix in lamellae around central canal
 Osteocytes in lacunae between lamellae
 Skeletal support; leverage for muscles; mineral
storage
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Blood

Variety of cells and cell fragments; some
with nuclei and some without
 Nonnucleated pale pink cells or nucleated
white blood cells
 Found in heart and blood vessels
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Nerve Tissue

Large cells with long cell processes


surrounded by smaller glial cells lacking processes
Internal communication between cells

in brain, spinal cord, nerves and ganglia
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Muscle Tissue
 Elongated
cells stimulated to contract
 Exert physical force on other tissues

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move limbs
push blood through a vessel
expel urine
 Source
of body heat
 3 histological types of muscle

skeletal, cardiac and smooth
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Skeletal Muscle

Long, cylindrical, unbranched cells with striations
and multiple peripheral nuclei

movement, facial expression, posture, breathing,
speech, swallowing and excretion
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Cardiac Muscle

Short branched cells with striations and
intercalated discs


one central nuclei per cell
Pumping of blood by cardiac (heart) muscle
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Smooth Muscle

Short fusiform cells; nonstriated with only one central nucleus
 sheets of muscle in viscera; iris; hair follicles and
sphincters
 swallowing, GI tract functions, labor contractions, control of
airflow, erection of hairs and control of pupil
40
Intercellular Junctions

All cells (except blood) anchored to each other
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or their matrix by intercellular junctions
Tight Junctions
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Encircle the cell joining it to surrounding cells

zipperlike complementary grooves and ridges
Prevents passage between cells

GI and urinary tracts
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Desmosomes
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Patch between cells holding them together

cells spanned by filaments terminating on protein plaque
• cytoplasmic intermediate filaments also attach to plaque
Uterus, heart and epidermis
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Gap Junctions

Ring of transmembrane proteins form a water-filled channel

small solutes pass directly from cell to cell

in embryos, cardiac and smooth muscle
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Endocrine and Exocrine Glands
 Secrete

substances
composed of epithelial tissue
 Exocrine
glands connect to surface with a
duct (epithelial tube)
 Endocrine glands secrete (hormones) directly
into bloodstream
 Mixed organs do both

liver, gonads, pancreas
 Unicellular

glands – endo or exocrine
goblet or intrinsic cells of stomach wall
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Exocrine Gland Structure
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
Stroma = capsule and septa divide gland into lobes and
lobules
Parenchyma = cells that secrete
Acinus = cluster of cells surrounding the duct draining
those cells
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Types of Exocrine Glands
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Simple glands - unbranched duct
Compound glands - branched duct
Shape of gland

acinar - secretory cells form dilated sac

tubuloacinar - both tube and sacs
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Types of Secretions
 Serous

glands
produce thin, watery secretions
• sweat, milk, tears and digestive juices
 Mucous

glands
produce mucin that absorbs water to form a sticky
secretion called mucus
 Mixed
glands contain both cell types
 Cytogenic glands release whole cells

sperm and egg cells
48
Holocrine Gland

Secretory cells disintegrate to deliver their
accumulated product

oil-producing glands of the scalp
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Merocrine and Apocrine Secretion

Merocrine glands release their
product by exocytosis
 tears, gastric glands,
pancreas, etc.
 Apocrine glands are merocrine
glands with confusing
appearance (apical cytoplasm
not lost)
 mammary and armpit sweat
glands
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Mucous Membranes


Epithelium, lamina propria and muscularis mucosae
Lines passageways that open to the exterior: reproductive, respiratory,
urinary and digestive

Mucous (movement of cilia) trap and remove foreign particles and
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bacteria from internal body surfaces
Membrane Types

Cutaneous membrane = skin



Synovial membrane lines joint cavities


stratified squamous epithelium over connective tissue
relatively dry layer serves protective function
connective tissue layer only, secretes synovial fluid
Serous membrane (serosa) –internal membrane


simple squamous epithelium over areolar tissue,
produces serous fluid
covers organs and lines walls of body cavities
52
Tissue Growth
 Hyperplasia
= tissue growth through cell
multiplication
 Hypertrophy = enlargement of preexisting
cells

muscle grow through exercise
 Neoplasia
= growth of a tumor (benign or
malignant) through growth of abnormal
tissue
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Tissue Repair
 Regeneration


replacement of damaged cells with original cells
skin injuries and liver regenerate
 Fibrosis

replacement of damaged cells with scar tissue
• function is not restored


healing muscle injuries, scarring of lung tissue in TB or
healing of severe cuts and burns of the skin
keloid is healing with excessive fibrosis (raised
shiny scars)
54
Wound Healing of a Laceration

Damaged vessels leak blood
 Damaged cells and mast
cells leak histamine
 dilates blood vessels
 increases blood flow
 increases capillary
permeability
 Plasma carries antibodies,
clotting factors and WBCs
into wound
55
Wound Healing of a Laceration

Clot forms
 Scab forms on
surface
 Macrophages
start to clean up
debris
56
Wound Healing of a Laceration



New capillaries grow
into wound
Fibroblasts deposit
new collagen to
replace old material
Fibroblastic phase
begins in 3-4 days
and lasts up to 2
weeks
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Wound Healing of a Laceration



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
Epithelial cells
multiply and spread
beneath scab
Scab falls off
Epithelium thickens
Connective tissue
forms only scar
tissue (fibrosis)
Remodeling phase
may last 2 years
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