Transcript Chapter 4-Tissues

Chapter 4
Tissue Level of Organization
Tissues are…
• Groups of similar cells and extracellular products that carry out a
common function
• providing protection
• facilitating body movement
• Study of tissues is histology
4 primary types of tissues in the body
• epithelial
• connective
• muscle
• nervous
today
later, dude
Epithelial Tissue
• Epithelial tissue covers or lines every body surface and body cavity
• Epithelium is composed of one or more layers of closely packed cells
between two compartments
Characteristics of Epithelial Tissue
1. Cellularity: composed almost entirely of cells (with some
extracellular matrix and sometimes other structures)
Characteristics of
Epithelial Tissue
2. Polarity: has specific top and
bottom
• apical surface exposed to
external environment or
internal body space, and
• basal surface attached to
underlying connective tissue,
plus
• lateral surfaces connected by
intercellular junctions
Apical (free) surface
Lateral
surface
Basal
surface
Epithelium
Basement
membrane
Connective
tissue
Blood
vessel
(a) Epithelium–connective tissue junction
Characteristics of Epithelial Tissue
4. Attachment: basal surface bound to basement membrane
5. Avascularity: no blood vessels; receive nutrients across apical
surface or by diffusion
6. Innervation: lots of nerve endings
7. High regeneration capacity: epithelial cells are frequently damaged
or lost to abrasion, so they are replaced quickly
Functions of Epithelial Tissue
• Physical protection: protect exposed and internal surfaces from
dehydration, abrasion, destruction
• Selective permeability: act as gatekeepers to let some substances in
and keep others out
• Sensation: sense changes in the environment
• Some also do secretion: contain glands that release sweat, scents,
hormones, etc.
Specialized structures
of Epithelial Tissue
• Basement layer is
extracellular layer between
epithelium and connective
tissue
Epithelium
Basement
membrane
Basal
surface
Connective
tissue
• often visible with microscope
(a) Epithelium–connective tissue junction
Fig. 4.1
Specialized structures
of Epithelial Tissue
• In some epithelial tissue, basal
cells anchored to basement
membrane with junctions
called hemidesmosomes
Hemidesmosome
Fig. 4.1
Intercellular Junctions
• Junctions between cells in
epithelium
• Tight junctions anchor cells to
each other
• prevents substances from passing
between cells
• materials must move through
cells, or are blocked from moving
past cells
• found in intestinal lining
Tight
junction
Fig. 4.1
Intercellular Junctions
• Adhering junctions often deep
to tight junctions
• Form all the way around a cell
• Support apical surface
• Allows passage between cells
below apical surface
Adhering
junction
Cell-Cell Attachment
• Desmosomes attach cells to each other
• Bind epithelium together
• Bind muscle cells
• Resist shear forces
Cell-Cell Communicating
Attachment
Cell
1
Cell
2
Cytosol
Channel proteins
Intercellular space
• Gap junctions tunnel between two
plasma membranes
• Found in muscles
• Enables sharing of ions and proteins
• Enables fast communication between cells
Cell membrane
Gap junctions are
communicating junctions.
Cell-Cell Communicating
Attachment
• Gap junctions tunnel between two
plasma membranes
• Found in muscles
• Enables sharing of ions and proteins
• Enables fast communication between
cells
Clusters of gap
junctions
Freeze fracture of cell membrane
Classifications of
Epithelial Tissue
• Number of cell layers
• simple = one cell layer thick
• stratified = >2 cell layers thick
Apical surface
Lateral surface
Basement
membrane
Basal surface
Simple epithelium
Apical surface
Lateral
surface
Basement
membrane
Basal surface
Stratified epithelium
Classifications of
Epithelial Tissue
Nucleus
Squamous cell
Nucleus
• Cell shape
• squamous = flattened
• cuboidal = basically cube-shaped or roundish
• columnar = long and thin (like a column)
Cuboidal cell
Nucleus
Columnar cell
Table 4.3a-1
Kidney tubules
Amnion
Simple
squamous cell
Simple
cuboidal
cell
LM 1000x
LM 400x
Simple squamous epithelium
Simple cuboidal epithelium
Table 4.3b-2
Mucosa of
small intestine
Uterine tube
Cilia
Nonciliated
simple
columnar cell
Simple
columnar
epithelial
cell
LM 400x
Nonciliated simple
columnar epithelium
LM 100x
Ciliated simple columnar
epithelium
Table 4.4a-1
Vagina
Epidermis of skin
Squamous
epithelial cell
Keratinized stratified
squamous epithelial cells
Nonkeratinized
stratified
squamous
epithelium
Living stratified
squamous epithelial cells
LM 125x
LM 100x
Table 4.4b-1
Male urethra
Duct of sweat gland
LM100x
Cuboidal cell
Stratified cuboidal
epithelium
Columnar cell
Stratified
columnar
epithelium
Table 4.5a
Nasal cavity lining
Cilia
Pseudostratified
ciliated columnar
epithelium
Columnar cell
Basal cell
• Pseudostratified columnar
epithelium looks stratified, but is
actually one layer of cells
• all cells in contact with basement
membrane
• stratified look because nuclei are at
different levels in cells
• may be ciliated or nonciliated
Table 4.5b
Urinary bladder lining
• Transitional epithelium is made of
cells that can stretch
• cells look cuboidal when relaxed; look
squamous when stretched
• found in lining of urinary bladder
Transitional
epithelium
(relaxed)
Binucleated
epithelial cell
Connective tissue
• Supports, protects, and binds organs
• Includes tendons and ligaments, body fat, cartilage, skeleton, blood
Connective tissue
• Contains
• specific types of cells
• protein fibers
• ground substance
• nonliving material of protein and carbohydrate molecules
form extracellular matrix (stuff
outside and around cells,
produced by cells)
• Each type of connective tissue has a specific function
• Develops from mesenchyme
• type of stem cell from which all other connective tissues arise
• first arises in developing embryo
Fig. 4.7
Ground
substance
Elastic fibers
Extracellular
matrix
Collagen fibers
Protein
fibers
Reticular fibers
Mesenchymal cell
Blood vessel
Macrophage
Adipocyte (fat cell)
Fibroblast
Loose connective tissue
• Fewer cells and protein fibers than dense connective tissue
• protein fibers loosely connected
Table 4.9a-1
Areolar connective tissue
Papillary layer of dermis
• Provides cushioning to overlying tissues
• Fibroblasts are most visible cells
Elastic fiber
• cells with tapered ends
• produce fibers and ground substance
• Has collagen fibers
• fibers of protein collagen
• strong, flexible, resistant to stretching
• Has elastic fibers
Fibroblast
Collagen fiber
Ground
substance
• fibers of protein elastin (thinner than collagen)
• stretch and recoil easily
LM 240x
Table 4.9a-2
Adipose connective tissue
• AKA “fat”
• contains large cells filled with a droplet of
lipid
• nucleus pushed to the side
• cushions structures from shocks
• acts as insulation
• storage of energy for the body
• adipocytes can’t divide, but mesenchyme
can make more if needed
Subcutaneous layer
(hypodermis)
Adipocyte
Blood
vessel
Adipocyte
nucleus
LM 250x
LM 200x
Dense connective tissue
• Primarily protein fibers
• lots of collagen fibers
• Less ground substance than loose connective tissue
• 3 types:
• dense regular
• tendons
• dense irregular
• reticular layer of dermis
• elastic
• wall of aorta
Table 4.10a-1
Dense, regular
connective tissue
• Found in tendons and ligaments
• Collagen fibers packed tightly,
arranged in parallel to force
applied
• Few blood vessels
Tendon
Ground
substance
Collagen
fibers
Fibroblast
nucleus
LM 250x
Table 4.10a-2
Dense, irregular
connective tissue
• Collagen fibers arranged in clumps
and bunches
Reticular layer
of dermis
Collagen fiber bundles
• scattered throughout tissue
• Withstands stress in all directions
• Found around cartilage and bone
• Forms capsule around some
internal organs
Fibroblast nucleus
Ground substance
LM 200x
Table 4.10b-1
Aorta wall
Elastic connective tissue
• Branching elastic fibers
• provide resilience and ability to
return to shape after being
deformed
• Lots of fibroblasts
• Collagen fibers packed close
Ground substance
Fibroblast nucleus
Elastic fibers