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Anatomy & Physiology I
Lecture 3
Chapter 4: Tissues
Tissues
• Cells
– Individual body cells specialized
– Each type performs specific functions that maintain
homeostasis
• Tissues
– Groups of cells similar in structure that perform
common or related function
• Histology – the study of tissues
Studying Human Tissue: Microscopy
• Tissue is fixed
– Preserved – FFPE or Fresh/Frozen
• Cut
– Sliced thin enough to transmit photons or
electrons
• Stained to enhance contrast
– H&E – Hematoxylin and eosin stain
– Immunohistochemisty
– Specific dye to highlight cells or structures
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H&E Stain
Colon tissue sectioned through the crypts
Immunohistochemistry
Stained for CD10, a marker for renal carcinoma
Figure 4.1 Overview of four basic tissue types: epithelial, connective, muscle, and nervous tissues.
Nervous tissue: Internal communication
• Brain
• Spinal cord
• Nerves
Muscle tissue: Contracts to cause movement
• Muscles attached to bones (skeletal)
• Muscles of heart (cardiac)
• Muscles of walls of hollow organs (smooth)
Epithelial tissue: Forms boundaries between different
environments, protects, secretes, absorbs, filters
• Lining of digestive tract organs and other hollow
organs
• Skin surface (epidermis)
Connective tissue: Supports, protects, binds
other tissues together
• Bones
• Tendons
• Fat and other soft padding tissue
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Epithelial Tissue
• Sheet of cells tht covers a body surface or
lines a body cavity
• Two main types (by location)
• Covering and lining epithelia
– On external and internal surfaces
• Glandular epithelia
– Secretory tissue in glands
Epithelial Tissue
• Forms boundaries
– Protection
– Absorption
– Filtration
– Excretion
– Secretion
– Sensory reception
Five Characteristics
• Polarity
– apical vs basal surface
• Specialized contacts
– tight junctions, desmosomes
• Supported by connective tissues
– for reinforcement
• Avascular, but innervated
• Can regenerate
Classification of Epithelia
• All epithelial tissues have two names
• First indicates number of cell layers
– Simple epithelia = single layer of cells
– Stratified epithelia = two or more layers of cells
• Second indicates shape of cells
– Squamous
– Cuboidal
– Columnar
Figure 4.2a Classification of epithelia.
Apical surface
Basal surface
Simple
Apical surface
Basal surface
Stratified
Classification based on number of cell layers.
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Figure 4.2b Classification of epithelia.
Squamous
Cuboidal
Columnar
Classification based on cell shape.
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Simple Epithelia
• Functions limited due to their thickness, but
nonetheless important
– Absorption
– Secretion
– Filtration
Figure 4.3a Epithelial tissues.
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 (140x).
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Simple Squamous
• Some have specialized names based on location:
• Endothelium
– The lining of lymphatic vessels, blood vessels, and
heart
• Mesothelium
– The epithelium of serous membranes in the ventral
body cavity
Figure 4.3c Epithelial tissues.
Simple columnar epithelium
Description: Single layer of tall cells
with round to oval nuclei; some cells
bear cilia; layer may contain mucussecreting unicellular glands (goblet
cells).
Microvilli
Simple
columnar
epithelial
cell
Function: Absorption; secretion of
mucus, enzymes, and other
substances; ciliated type propels
mucus (or reproductive cells) by ciliary
action.
Mucus of
goblet cell
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.
Basement
membrane
Photomicrograph: Simple columnar
epithelium of the small intestine mucosa (660x).
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Figure 4.3d Epithelial tissues.
Pseudostratified columnar epithelium
Description: Single layer of cells of
differing heights, some not reaching
the free surface; nuclei seen at
different levels; may contain mucussecreting cells
and bear cilia.
Cilia
Pseudostratified
epithelial
layer
Function: Secrete substances,
particularly mucus; propulsion of
mucus by ciliary action.
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
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Photomicrograph: Pseudostratified
ciliated columnar epithelium lining the human
trachea (800x).
Basement
membrane
Figure 4.3e Epithelial tissues.
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.
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Nuclei
Basement
membrane
Connective
tissue
Photomicrograph: Stratified squamous
epithelium lining the esophagus (285x).
Other Stratified Epithelia
• Stratified cuboidal and stratified columnar are
rare and limited to specialized parts of body
– pharynx, male urethra, some glandular ducts,
sweat and mammary glands
Figure 4.3f Epithelial tissues.
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
Function: Stretches readily, permits
stored urine to distend urinary organ.
Location: Lines the ureters,
bladder, and part of the urethra.
Photomicrograph: Transitional epithelium lining
the bladder, relaxed state (360x); note the bulbous, or
rounded, appearance of the cells at the surface; these
cells flatten and elongate when the bladder fills with
urine.
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Basement
membrane
Connective
tissue
Glandular Epithelia
• Gland
– One or more cells that makes and secretes an
aqueous fluid called a secretion
• Classified by
– Site of product release—endocrine or exocrine
– Relative number of cells forming the gland
– Unicellular or multicellular
Endocrine Glands
• Ductless glands
– Secretions not released into a duct, but via
exocytosis
• Secrete hormones that travel through lymph
or blood to their specific target organs
– every hormone has a specific target cell for a
specific physiological response
Exocrine Glands
• Secretions released onto body surfaces (skin)
or into body cavities
– mucous, sweat, oil, and salivary glands, digestive
juices
• More numerous than endocrine glands
• Secrete products into ducts
Unicellular Glands
• Mucous cells and Goblet cells
• Found in epithelial linings of intestinal and
respiratory tracts
– All produce mucin
– Dissolves in water to form mucus
– Slimy protective, lubricating coating
Figure 4.4 Goblet cell (unicellular exocrine gland).
Microvilli
Secretory
vesicles
containing
mucin
Golgi
apparatus
Rough ER
Nucleus
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Multicellular Exocrine Glands
• Multicellular exocrine glands are more
complex and specialized for the function
• Pancreas and Liver have exocrine functions
despite their other roles
Connective Tissue
• Most abundant and widely distributed of
primary tissues
• Four main classes
– Connective tissue proper
– Cartilage
– Bone
– Blood
Major Functions
•
•
•
•
•
Binding and support
Protecting
Insulating
Storing reserve fuel
Transporting substances (blood)
Connective Tissue Elements
• Ground Substance
• Tissue Fibers
Ground Substance
• Extracellular maxtix
• Unstructured material that fills space between cells
– white blood cells and immune cells migrate
• Components
– Interstitial fluid
– Cell adhesion proteins ("glue" for attachment)
– Proteoglycans
• Protein core + large polysaccharides that trap water in varying
amounts, affecting viscosity of ground substance
Connective Tissue Fibers
• Collagen
– Strongest and most abundant type
• Elastic fibers
– Networks of long, thin, elastin fibers that allow for
stretch and recoil
• Reticular
– Short, fine, highly branched collagenous-like fibers
– Form networks that offer support and elasticity
Connective Tissue Cells
• "Blast" cells – Immature form; mitotically active;
secrete ground substance and fibers
–
–
–
–
Fibroblasts in connective tissue proper
Chondroblasts in cartilage
Osteoblasts in bone
Hematopoietic stem cells in bone marrow
• "Cyte" cells – Mature form; maintain matrix
– Chondrocytes in cartilage
– Osteocytes in bone
Connective Tissue Proper
• Loose Connective Tissue
– Areolar
– Adipose
– Reticular
• Dense Connective Tissue
– Regular
– Irregular
– Elastic
Figure 4.8a Connective tissues.
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.
Function: Wraps and cushions
organs; its macrophages phagocytize
bacteria; plays important role in
inflammation; holds and conveys
tissue fluid.
Elastic
fibers
Ground
substance
Location: Widely distributed under
epithelia of body, e.g., forms lamina
propria of mucous membranes;
packages organs; surrounds capillaries.
Fibroblast
nuclei
Collagen
fibers
Epithelium
Lamina
propria
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Photomicrograph: Areolar connective
tissue, a soft packaging tissue of the body (340x).
Figure 4.8b Connective tissues.
Connective tissue proper: loose connective tissue, adipose
Description: Matrix as in areolar, but
very sparse; closely packed adipocytes,
or fat cells, have nucleus pushed to the
side by large fat droplet.
Function: Provides reserve food fuel;
insulates against heat loss; supports and
protects organs.
Nucleus of
adipose
(fat) cell
Location: Under skin in
subcutaneous tissue; around kidneys
and eyeballs; within abdomen; in
breasts.
Adipose
tissue
Fat droplet
Photomicrograph: Adipose tissue from
the subcutaneous layer under the skin (350x).
Mammary
glands
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Figure 4.8c Connective tissues.
Connective tissue proper: loose connective tissue, reticular
Description: Network of reticular
fibers in a typical loose ground
substance; reticular cells lie on the
network.
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
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Photomicrograph: Dark-staining network of
reticular connective tissue fibers forming the
internal skeleton of the spleen (350x).
Figure 4.8d Connective tissues.
Connective tissue proper: dense connective tissue, dense regular
Description: Primarily parallel
collagen fibers; a few elastic fibers;
major cell type is the fibroblast.
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
Tendon
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Photomicrograph: Dense regular connective
tissue from a tendon (430x).
Figure 4.8e Connective tissues.
Connective tissue proper: dense connective tissue, dense irregular
Description: Primarily irregularly
arranged collagen fibers; some
elastic fibers; fibroblast is the
major cell type.
Nuclei of
fibroblasts
Function: Withstands 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
Shoulder
joint
Fibrous
joint
capsule
Photomicrograph: Dense irregular connective
tissue from the fibrous capsule of a joint (430x).
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Figure 4.8f Connective tissues.
Connective tissue proper: dense connective tissue, elastic
Description: Dense regular
connective tissue containing a
high proportion of elastic fibers.
Function: Allows tissue to recoil
after 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
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Photomicrograph: Elastic connective tissue
in the wall of the aorta (250x).
Cartilage
• Cells:
– Chondroblasts and chondrocytes
• Tough yet flexible
– Up to 80% water - can rebound after compression
• Lacks nerve fibers and blood vessels
(avascular)
Cartilage
• Hyaline
• Elastic
• Fibrocartilage
Figure 4.8g Connective tissues.
Cartilage: hyaline
Description: Amorphous but firm
matrix; collagen fibers form an
imperceptible network;
chondroblasts produce the matrix
and when mature (chondrocytes)
lie in lacunae.
Function: Supports and reinforces;
serves as resilient cushion; resists
compressive stress.
Chondrocyte
in lacuna
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
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Matrix
Photomicrograph: Hyaline cartilage from
a costal cartilage of a rib (470x).
Figure 4.8h Connective tissues.
Cartilage: elastic
Description: Similar to hyaline
cartilage, but more elastic fibers
in matrix.
Function: Maintains the shape of
a structure while allowing great
flexibility.
Chondrocyte
in lacuna
Matrix
Location: Supports the external
ear (pinna); epiglottis.
Photomicrograph: Elastic cartilage from
the human ear pinna; forms the flexible
skeleton of the ear (800x).
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Figure 4.8i Connective tissues.
Cartilage: fibrocartilage
Description: Matrix similar to but
less firm than that in hyaline
cartilage; thick collagen fibers
predominate.
Function: Tensile strength allows
it 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 (125x). Special staining
produced the blue color seen.
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Bone – Osseous Tissue
• Supports and protects body structures
– Stores fat and synthesizes blood cells in cavities
– More collagen than cartilage
– Has inorganic calcium salts
• Osteoblasts produce matrix
• Osteocytes maintain the matrix
• Richly vascularized
Figure 4.8j Connective tissues.
Others: bone (osseous tissue)
Description: Hard, calcified
matrix containing many collagen
fibers; osteocytes lie in lacunae.
Very well vascularized.
Function: 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 (125x).
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Blood
• Atypical connective tissue – is a fluid
• Red blood cells most common cell type that
function in transport
– Also contains white blood cells and platelets
• Fibers are soluble proteins that precipitate
during blood clotting
Figure 4.8k Connective tissues.
Connective tissue: blood
Description: Red and white blood
cells in a fluid matrix (plasma).
Red blood
cells
(erythrocytes)
Function: Transport respiratory
gases, nutrients, wastes, and other
substances.
White blood
cells:
• Lymphocyte
• Neutrophil
Location: Contained within blood
vessels.
Plasma
Photomicrograph: Smear of human blood
(1670x); shows two white blood cells
surrounded by red blood cells.
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Muscle
• Responsible for most types of movement
– Highly vascularized
• Skeletal muscle tissue
– Voluntary
• Cardiac muscle tissue
– Involuntary
• Smooth muscle tissue
– Involuntary
Figure 4.9a Muscle tissues.
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. 440x). Notice the obvious banding
pattern and the fact that these large cells are
multinucleate.
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Figure 4.9b Muscle tissues.
Cardiac muscle
Description: Branching, striated,
generally uninucleate cells that
interdigitate at specialized
junctions (intercalated discs).
Intercalated
discs
Function: As it contracts, it
propels blood into the circulation;
involuntary control.
Striations
Location: The walls of the heart.
Nucleus
Photomicrograph: Cardiac muscle (900x);
notice the striations, branching of cells, and
the intercalated discs.
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Figure 4.9c Muscle tissues.
Smooth muscle
Description: Spindle-shaped
cells with central nuclei; no
striations; cells arranged closely
to form sheets.
Function: Propels substances or
objects (foodstuffs, urine, a baby)
along internal passageways;
involuntary control.
Nuclei
Location: Mostly in the walls of
hollow organs.
Smooth
muscle
cell
Photomicrograph: Sheet of smooth
muscle (720x).
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Nervous Tissue
• Main component of nervous system
• Brain, spinal cord, nerves
– Regulates and controls body functions
• Neurons
– Specialized nerve cells that generate and conduct nerve
impulses
• Neuroglia
– Supporting cells that support, insulate, and protect neurons
Figure 4.10 Nervous tissues.
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) which control their
activity; supporting cells support
and protect neurons.
Neuron
processes
Location: Brain, spinal
cord, and nerves.
Photomicrograph: Neurons (350x).
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Lining Membranes
• Composed of at least two primary tissue types
– An epithelium bound to underlying connective
tissue proper
• Three types
– Cutaneous membranes
– Mucous membranes
– Serous membranes
– Synovial membrane (connective tissue only, Ch. 8)
Cutaneous Membrane
• Skin
– Keratinized stratified squamous epithelium
(epidermis) attached to a thick layer of connective
tissue (dermis)
• The only dry membrane
Mucous Membranes
• Epithelial sheet lies over layer of connective
tissue called lamina propria
• Line body cavities open to the exterior
– Digestive, respiratory, urogenital tracts
• Mucosa indicates location not cell
composition
– All called mucosae
Figure 4.11b Classes of membranes.
Mucous membranes
Mucous membranes line body
cavities that are open to the
exterior.
Mucosa of
nasal cavity
Mucosa of
mouth
Esophagus
lining
Mucosa of
lung bronchi
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Serous Membranes
• Serosae—found in closed ventral body cavity
• Simple squamous epithelium (mesothelium)
resting on thin areolar connective tissue
• Parietal serosae line internal body cavity walls
• Visceral serosae cover internal organs
• Serous fluid between layers
Figure 4.11c Classes of membranes.
Serous membranes
Serous membranes line body cavities that are
closed to the exterior.
Parietal
pleura
Visceral
pleura
Parietal
pericardium
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Visceral
pericardium
Parietal
peritoneum
Visceral
peritoneum
Today’s Lab
• Lab Exercise 6
• Learn to identify tissue under the microscope
and understand their general functions