Transcript Exercise 6 Classification of Tissues

Classification of Tissues


Group of cells
Similar structure & function




Epithelial
Connective
Muscle
Nervous

Cover surfaces

Simple or stratified?
Apical surface
Basal
surface
◦ Simple
Simple
Apical surface
◦ Stratified
◦ Apical vs. basal
Basal
surface
Stratified
Squamous
Simple squamous
Stratified squamous
Simple cuboidal
Cuboidal
Stratified cuboidal
Simple columnar
Stratified columnar
Columnar
Simple squamous epithelium

Simple squamous epithelium
Description: Single layer of flattened cells
with disc-shaped central nuclei and sparse
cytoplasm; the simplest of the epithelia.
Air sacs of
lung tissue
Nuclei
of squamous
epithelial
cells
Function: Allows materials to pass by
diffusion and filtration in sites where
protection is not important; secretes
lubricating substances in serosae.
Location: Kidney glomeruli; air sacs of
lungs; lining of heart, blood vessels, and
lymphatic vessels; lining of ventral body
cavity (serosae).
Photomicrograph: Simple squamous epithelium
forming part of the alveolar (air sac) walls (140).
Simple cuboidal epithelium

Simple cuboidal epithelium
Description: Single layer of cubelike
cells with large, spherical central
nuclei.
Simple
cuboidal
epithelial
cells
Function: Secretion and absorption.
Basement
membrane
Location: Kidney tubules; ducts and
secretory portions of small glands;
ovary surface.
Connective
tissue
Photomicrograph: Simple cuboidal epithelium
in kidney tubules (430).
Fig 4-4
Simple columnar epithelium

Simple columnar epithelium
Description: Single layer of tall cells with
round to oval nuclei; some cells bear cilia;
layer may contain mucus-secreting
unicellular glands (goblet cells).
Goblet cells
Mucus
secretion
Function: Absorption; secretion of mucus,
enzymes, and other substances; ciliated
type propels mucus (or reproductive cells)
by ciliary action.
Location: Nonciliated type lines most of
the digestive tract (stomach to rectum),
gallbladder, and excretory ducts of some
glands; ciliated variety lines small bronchi,
uterine tubes, and some regions of the
uterus.
Microvilli
(brush border)
Photomicrograph: Simple columnar epithelium containing
goblet cells from the small intestine (640).
Pseudostratified columnar epithelium

Pseudostratified columnar epithelium
Description: Single layer of cells of differing
heights, some not reaching the free surface;
nuclei seen at different levels; may contain
mucus-secreting goblet cells and bear cilia.
Mucus of
goblet cell
Cilia
Function: Secretes substances, particularly
mucus; propulsion of mucus by ciliary action.
Pseudostratified
epithelial
layer
Location: Nonciliated type in male’s
sperm-carrying ducts and ducts of large
glands; ciliated variety lines the trachea,
most of the upper respiratory tract.
Trachea
Basement
membrane
Photomicrograph: Pseudostratified ciliated
columnar epithelium lining the human trachea (530).
Fig 4-5
Stratified squamous epithelium

Stratified squamous epithelium
Description: Thick membrane composed of
several cell layers; basal cells are cuboidal or
columnar and metabolically active; surface
cells are flattened (squamous); in the
keratinized type, the surface cells are full of
keratin and dead; basal cells are active in
mitosis and produce the cells of the more
superficial layers.
Stratified
squamous
epithelium
Function: Protects underlying tissues in
areas subjected to abrasion.
Location: Nonkeratinized type forms the
moist linings of the esophagus, mouth, and
vagina; keratinized variety forms the
epidermis of the skin, a dry membrane.
Nuclei
Basement
membrane
Connective
tissue
Photomicrograph: Stratified squamous epithelium
lining the esophagus (280).
Stratified cuboidal epithelium
Stratified cuboidal epithelium

Description:
Generally two
layers of cubelike cells.
Basement
membrane
Cuboidal
epithelial
cells
Function: Protection
Location: Largest ducts of
sweat glands, mammary
glands, and salivary glands.
Duct
lumen
Photomicrograph: Stratified cuboidal
epithelium forming a salivary gland
duct (290).
Stratified columnar epithelium
Stratified columnar epithelium

Description:
Several cell layers;
basal cells usually cuboidal;
superficial cells elongated
and columnar.
Basement
membrane
Stratified
columnar
epithelium
Function: Protection; secretion.
Location: Rare in the body; small
amounts in male urethra and in
large ducts of some glands.
Urethra
Connective
tissue
Photomicrograph: Stratified columnar epithelium
lining of the male urethra (290).
Fig 4-5
Transitional epithelium
Description: Resembles both stratified
squamous and stratified cuboidal; basal
cells cuboidal or columnar; surface cells
dome shaped or squamouslike, depending
on degree of organ stretch.

Transitional epithelium
◦ Stratified squamous epithelium formed of
rounded cells that can slide over one
another, allowing the organ to stretch:
urinary system only
Transitional
epithelium
Function: Stretches readily and permits
distension of urinary organ by contained
urine.
Location: Lines the ureters, urinary
bladder, and part of the urethra.
Basement
membrane
Photomicrograph: Transitional epithelium lining the urinary
bladder, relaxed state (365); note the bulbous, or rounded,
appearance of the cells at the surface; these cells flatten and
become elongated when the bladder is filled with urine.
Connective
tissue

Embryonic connective tissue
◦ mesenchyme

Loose connective tissue
◦ Areolar, adipose, reticular

Dense connective tissue
◦ Dense irregular, dense regular

Supportive connective tissue
◦ Hyaline, elastic, fibrocartilages; bone

Fluid connective tissue
◦ Blood, lymph
Figure 6.4 Areolar connective tissue: A prototype (model) connective tissue.
Cell types
Extracellular
matrix
Ground substance
Macrophage
Fibers
• Collagen fiber
• Elastic fiber
• Reticular fiber
Fibroblast
Lymphocyte
Fat cell
Mast cell
Neutrophil
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Capillary

Differing proportions of cells & fibers to
“matrix”
◦ Matrix
 noncellular, nonliving material between
connective tissue cells
◦ Different proportions  strength of
tissue
Fig. 4-8
Many cell types
Distinct cell types
Less diverse cell types
Syrupy ground substance
Watery matrix
More fibrous matrix
Embryonic connective tissue: Mesenchyme
Mesenchyme
 Embryonic connective
Description:
tissue; gel-like ground substance
containing fibers; star-shaped
mesenchymal cells.
◦ Many star-shaped stem cells
◦ Gives rise to all other connective tissues
Function: Gives rise to all other
connective tissue types.
◦ Not present in adults
Location: Primarily in embryo.
Fibers
Ground
substance
Mesenchymal
cell
Photomicrograph: Mesenchymal tissue, an embryonic
connective tissue (627); the clear-appearing background is
the fluid ground substance of the matrix; notice the fine,
sparse fibers.)
Connective tissue proper: loose connective tissue, areolar
Description: Gel-like matrix with all
three fiber types; cells: fibroblasts,
macrophages, mast cells, and some
white blood cells.
Collagen
fibers
Function: Wraps and cushions organs;
its macrophages phagocytize bacteria;
plays important role in inflammation;
holds and conveys tissue fluid.
Fibroblast
nuclei
Location: Widely distributed under
epithelia of body, e.g., forms lamina
propria of mucous membranes;
packages organs; surrounds capillaries.
Elastic
fibers
Epithelium
Lamina
propria
Photomicrograph: Areolar connective tissue, a soft packaging
tissue of the body (365).
Connective tissue proper: loose connective tissue, adipose
Adipose connective tissue
Description:
 Matrix as in areolar,
but very sparse; closely packed
adipocytes, or fat cells, have
nucleus pushed to the side by
large fat droplet.
◦ (fat)
◦ Insulation for the body’s tissues
Function: Provides
reserve
fuel;
◦ Food
storage
insulates against heat loss;
supports and◦protects
Littleorgans.
matrix
Location: Under skin; around
kidneys and eyeballs; within
abdomen; in breasts.
Vacuole
containing
fat droplet
Nuclei of
fat cells
Photomicrograph: Adipose tissue from the
subcutaneous layer under the skin (110).
Connective tissue proper: loose connective tissue, reticular
Reticular connective tissue
Description:
 Network of reticular
fibers in a typical loose ground
substance; reticular cells lie on
the network.
◦ Reticular fibers form a soft internal skeleton
for support
Function: Fibers form a soft
internal skeleton (stroma) that
supports other cell types,
including white blood cells, mast
cells, and macrophages.
White
blood cell
(lymphocyte)
Location: Lymphoid organs
(lymph nodes, bone marrow,
and spleen).
Reticular
fibers
Spleen
Photomicrograph: Dark-staining network of
reticular connective tissue fibers forming the
internal skeleton of the spleen (350).
Connective tissue proper: dense connective tissue, dense irregular
Description: Primarily irregularly
arranged collagen fibers; some elastic
fibers; major cell type is the fibroblast.
Nuclei of
fibroblasts
Function: Able to withstand tension
exerted in many directions; provides
structural strength.
Location: Fibrous capsules of organs
and of joints; dermis of the skin;
submucosa of digestive tract.
Collagen
fibers
Fibrous
joint
capsule
Photomicrograph: Dense irregular connective
tissue from the dermis of the skin (210).
Connective tissue proper: dense connective tissue, dense regular
Dense regular connective tissue
Description:
 Primarily parallel
collagen fibers; a few elastic fibers;
major cell type is the fibroblast.
◦ Fibers in one direction
◦ Tendons, ligaments of body’s joints
Function: Attaches muscles to bones
or to muscles; attaches bones to bones;
withstands great tensile stress when
pulling force is applied in one direction.
Collagen
fibers
Location: Tendons, most
ligaments, aponeuroses.
Nuclei of
fibroblasts
Shoulder
joint
Ligament
Photomicrograph: Dense regular connective tissue
from a tendon (590).
Tendon
Fig. 4-12
Connective tissue proper: dense connective tissue, elastic
Description: Dense regular connective
tissue containing a high proportion of
elastic fibers.
Function: Allows recoil of tissue
following stretching; maintains
pulsatile flow of blood through
arteries; aids passive recoil of lungs
following inspiration.
Location: Walls of large arteries;
within certain ligaments associated
with the vertebral column; within the
walls of the bronchial tubes.
Elastic
fibers
Aorta
Heart
Photomicrograph: Elastic connective tissue in the
wall of the aorta (250).
Cartilage: hyaline
Description: Amorphous but firm matrix;
collagen fibers form an imperceptible
network; chondroblasts produce the
matrix and when mature (chondrocytes)
lie in lacunae.
Chondrocyte
in lacuna
Function: Supports and reinforces;
serves as resilient cushion; resists
compressive stress.
Location: Forms most of the embryonic
skeleton; covers the ends of long bones
in joint cavities; forms costal cartilages
of the ribs; cartilages of the nose,
trachea, and larynx.
Costal
cartilages
Matrix
Photomicrograph: Hyaline cartilage from a costal
cartilage of a rib (470).
Elastic Cartilage
Cartilage: elastic

Description: Similar to hyaline
cartilage, but more elastic
fibers in matrix.
◦ Maintains shape, but flexible
◦ Many elastic fibers
Function: Maintains the shape
of a structure while allowing
great flexibility.
Chondrocyte
in lacuna
Location: Supports the external
ear (auricle); epiglottis.
Matrix
Photomicrograph: Elastic cartilage from the
human ear auricle; forms the flexible skeleton
of the ear (510).
Cartilage: fibrocartilage

Fibrocartilage
Description: Matrix similar to
but less firm than that in hyaline
cartilage; thick collagen fibers
predominate.
◦ Strength, shock absorption
◦ Dense network of collagen fibers
Function: Tensile strength with
the ability to absorb compressive
shock.
Location: Intervertebral discs;
pubic symphysis; discs of knee
joint.
Chondrocytes
in lacunae
Intervertebral
discs
Collagen
fiber
Photomicrograph: Fibrocartilage of an intervertebral
disc (160). Special staining produced the blue color seen.
Bones (osseous tissue)
Osseous Connective Tissue (Bone)

Description:
Hard, calcified matrix
containing many collagen fibers;
osteocytes lie in lacunae. Very
well vascularized.
◦ Support, protection
Function: Bone supports and
protects (by enclosing); provides
levers for the muscles to act on;
stores calcium and other minerals
and fat; marrow inside bones is the
site for blood cell formation
(hematopoiesis).
Central
canal
Lacunae
Lamella
Location: Bones
Photomicrograph: Cross-sectional view of bone (175).
Blood
Description: Red and white
blood cells in a fluid matrix
(plasma).
Function: Transport of
respiratory gases, nutrients,
wastes, and other substances.
Location: Contained within
blood vessels.
Plasma
Neutrophil
Red blood
cells
Lymphocyte
Photomicrograph: Smear of human blood (1000);
two white blood cells (neutrophil and lymphocyte) are
seen surrounded by red blood cells.

Lymph
◦ Fluid of the lymphatic system
◦ Like plasma without the big proteins
◦ Immune defense



Skeletal
Cardiac
Smooth
Skeletal muscle
Description: Long, cylindrical,
multinucleate cells; obvious
striations.
Part of
muscle
fiber (cell)
Function: Voluntary movement;
locomotion; manipulation of the
environment; facial expression;
voluntary control.
Nuclei
Location: In skeletal muscles
attached to bones or occasionally
to skin.
Striations
Photomicrograph: Skeletal muscle (approx. 550).
Notice the obvious banding pattern and the
fact that these large cells are multinucleate.
Cardiac muscle
Only in the heart
Striated tissue
Nucleus
 Under involuntary control
Intercalated
discs

Branching,
uninucleate
cells
with
intercalated
Function: As it contracts, it
Description:
Branching, striated,

generally uninucleate cells that
interdigitate
 at specialized junctions
called intercalated discs.
discs
propels blood into the circulation;
involuntary control.
Striations
Location: The walls of the heart.
Photomicrograph: Cardiac muscle (775);
notice the striations, branching of cells, and
the intercalated discs.
Smooth muscle
Found in the walls of hollow organs
(digestive, urinary tracts; blood vessels)
 2 layers at right angles for
contraction/dilation of the organ cavity Smooth
Function: Propels substances or
muscle
objects (foodstuffs, urine, a baby)

Not
striated
tissue
cell
along internal passageways;
involuntary control.
Nucleus
 Uninucleate, spindle-shaped cells

Description:
Spindle-shaped cells
with central nuclei; no striations;
cells arranged closely to form
sheets.
Location: Mostly in the walls of
hollow organs.
Photomicrograph: Smooth muscle cells (265).
Muscle type
Cells
striations
Voluntary?
Cardiac
branched
Uninucleate
Intercalated discs
yes
no
Skeletal
Long fibers
multinucleate
yes
yes
Smooth
Spindle shaped
1 nucleus
no
no


Brain, spinal cord, nerves
2 basic cell types:
◦ Neuroglia cells
 Protect, support, insulate neurons
◦ Neurons
 Receive stimuli & conduct nerve impulses
Nervous tissue
Description: Neurons are branching
cells; cell processes that may be quite
long extend from the nucleus-containing
cell body; also contributing to nervous
tissue are nonexcitable supporting cells.
Neuron processes
Nuclei of
supporting
cells
Cell body
Axon Dendrites
Cell body
of a neuron
Function: Neurons transmit electrical
signals from sensory receptors and to
effectors (muscles and glands); supporting
cells support and protect neurons.
Neuron
processes
Location: Brain, spinal
cord, and nerves.
Photomicrograph: Neurons (370)
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