2/14/2012
The Study of Tissues
Today’s Objectives
• 50 trillion cells of 200 different cell types
• Tissues: Group of similar cells
– common embryonic origin
– common function
1. Learn the 4 types of tissues
2. Understand the origins of all tissues
3. Know the general features of
- epithelial tissue
- nervous tissue
4. Lab
• 4 broad categories of tissues
– epithelial tissue
– connective tissue
– nervous tissue
– muscular tissue
• organ – Two or more tissues working together common
function
• histology (microscopic anatomy) – the study of tissues
3-1
Sectioning Solid Objects
5-2
Sectioning Hollow Structures
• cross section of
blood vessel, gut,
or other tubular
organ.
• sectioning a cell
with a centrally
located nucleus
• some slices
miss the cell
nucleus
• longitudinal
section of a
sweat gland.
notice what a
single slice could
look like.
• in some the
nucleus is
smaller
(c)
(b)
(a)
5-3
Figure 5.1a
Figure 5.1b,c
Tissue Sections
5-4
4 Primary Tissues
Longitudinal sections
• longitudinal section (l.s.)
1.
Epithelial Tissue:
– covers surfaces
– lines hollow organs, cavities and ducts
– forms glands (beneath surface)
2.
Connective Tissue:
– supports - binds structures together
– stores energy as fat
– provides immunity to disease
– transports things
– tissue cut along long direction of
organ
Cross sections
• cross section (c.s. or x.s.) or
transverse section (t.s.)
– tissue cut perpendicular to
length of organ
Oblique sections
• oblique section
– tissue cut at angle between
cross and longitudinal section
5-5
3-6
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Origin of Tissues
4 Primary Tissues
• Primary germ layers within the embryo
3. Muscle Tissue:
–
–
4.
– Endoderm
– Mesoderm
– Ectoderm
cells shorten in length producing movement
produce kinetic energy
Nerve Tissue:
– cells that conduct electrical signals
– detect stimuli inside and outside the body
– communication
• Tissue derivations
– G.I. Tract, respiratory tract, Urinary from
Endoderm
– connective tissue & muscle from mesoderm
– nerve tissue and epidermis from ectoderm
3-7
3-8
Cell Junctions
1.
Epithelial Tissue -- General Features
•
•
•
•
Gap Junction
1. Anchor
2. Form seals between cells
3. Provide channels
Hemidesmosomes
Tight junctions
Desmosomes
Closely packed cells
Cells sit on basement membrane (extracellular layer)
Apical surface (upper free surface)
Avascular---without blood vessels
– nutrients diffuse in from underlying connective
tissue
• Good nerve supply
• Rapid cell division
Adherens
junctions
3-9
Basement Membrane
• Basal lamina
– from epithelial cells
– collagen fibers
– Adhesive
glycoproteins
(laminin)
• Reticular lamina
– secreted by
connective tissue
cells
– reticular fibers
– Collegen fibers
• holds cells to connective
tissue
3-11
3-10
Two Types of Epithelium
1.
Covering and lining epithelium
– epidermis of skin
– lines blood vessels and ducts
– lines respiratory, reproductive, urinary & GI
tracts
2. Glandular epithelium
– secreting portion of glands
3-12
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Examples
Classification of Epithelium
• Layers of cells
– simple = one cell layer thick
– stratified = many cell layers thick
– pseudostratified = single layer of cells where all cells
don’t reach apical surface
- nuclei at different levels - looks multilayered
• Shape of surface cells
– squamous = flat
– cuboidal = cube-shaped
– columnar = tall column
– transitional = shape varies with tissue stretching
by
layers
by
shape
3-13
Figure 4.1a
3-14
(a)
Classes of
epithelium
(b)
Cell
shapes
5-16
Figure 5.3
Simple Cuboidal Epithelium
Simple Squamous Epithelium
• Single layer of flat cells
• e.g., lines
blood vessels &
body cavities
3-17
3-18
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Ciliated Simple Columnar Epithelium
Nonciliated Simple Columnar
• Single layer rectangular cells
• Unicellular glands =goblet cells secrete mucus
– lubricate GI, respiratory, and urinary systems
• Microvilli
• Single layer rectangular cells with cilia
• Mucus from goblet cells moved along by cilia
3-19
3-20
Stratified Squamous Epithelium
Pseudostratified Columnar
• Several cell layers
thick
• Surface cells flat
•
•
•
•
Single cell layer
Not all cells reach apical surface
Nuclei at varying depths
Respiratory system, male urethra & epididymis
3-21
3-22
Stratified Cuboidal Epithelium
Stratified Squamous
Living epithelial cells
(a)
Connective tissue
(b)
a: © Ed Reschke
Figure 5.9b,i
• Multilayered
• Surface cells cuboidal
– rare
5-23
3-24
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Stratified Columnar Epithelium
• Multilayered
• Surface cells columnar
• Rare
Transitional Epithelium
• Multilayered
• Surface cells vary in shape
• Lines hollow organs that expand from within
3-25
3-26
Glandular Epithelium
Goblet Cell
• Derived from epithelial cells
• Exocrine glands (glands with ducts)
– cells that secrete onto free surface of
epithelial layer
• Endocrine glands (glands without ducts)
– secrete hormones into the bloodstream
Figure 4.3b
3-27
Glandular Epithelium
Classification of Exocrine Glands
Exocrine
glands
Single-celled glands: Goblet cells
Multicellular glands:
- unbranched = simple
- branched = compound
•
1.
2.
3.
Tubular vs. rounded secretory parts
Tubular = tubular
Acinar = rounded (flask-like shape)
Tubuloacinar = both tubular & rounded shapes
Endocrine
glands
3-29
3-30
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Types of Exocrine Glands
Simple coiled tubular
Compound acinar
Types of Secretions
• serous glands
Compound tubuloacinar
– produce thin, watery secretions
• perspiration, milk, tears and digestive juices
• mucous glands
– produce glycoprotein, mucin, that absorbs water to form a
sticky secretion called mucus
– goblet cells – unicellular mucous glands
Example: Sweat gland
Example: Pancreas
Key
Example: Mammary gland
Duct
• mixed glands
Secretory portion
• simple - unbranched duct
• compound - branched duct
• shape of gland
– contain both cell types and produce a mixture of the two
types of secretions
– tubular – duct and secretory portion have uniform diameter
– acinar - secretory cells form dilated sac (acinus or alveolus)
– tubuloacinar - both tubular and acinar portions
• cytogenic glands
– release whole cells, sperm and egg cells
5-31
5-32
Methods of Secretion
Holocrine Gland
Methods of Secretion
Merocrine Gland
• merocrine glands (eccrine
glands) – vesicles release
secretion by exocytosis
Figure 5.31b
– tear glands, pancreas, gastric
glands, and others
• apocrine glands – primarily
merocrine mode of secretion
Exocytosis
Nucleus
(b) Holocrine gland
– axillary sweat glands, mammary
glands
• holocrine glands – product synthesized then the cell
disintegrates
Secretory
vesicle
(a) Merocrine gland
Figure 5.31a
5-33
– secretion a mixture of cell fragments and synthesized
substance
– oil glands of scalp, glands of eyelids
5-34
Nerve Tissue
Methods of
Glandular
Secretion
• Cell types -- neurons and neuroglial (supporting) cells
• Nerve cell structure: Cell body, Dendrites, axons
• Action potential - neurotransmitter
3-35
3-36
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