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TISSUES
HISTOLOGY = THE STUDY OF TISSUES
What is a tissue?
• Atoms make up molecules
• Molecules make up cells
• Cells make up tissues
• Tissues make up organs (groups of cells with a common function)
• Organs make up organ systems
• Organ systems make up organisms
© 2015 Pearson Education, Inc.
4 Tissue Types in the Human Body:
• Epithelial – linings
• Connective – connect body parts
• Muscle – movement
• Nervous – involved with signal transmission
6 Epithelial Tissue Characteristics
1) Cellularity
• Cells are bound close together
• No intercellular space
2) Polarity
• Have an exposed apical surface
• Have an attached basal surface
• Surfaces are structurally and
functionally different
• Polarity is the term that is in
reference to this structural and
functional difference
3) Attachment
• Basal layer is attached to the
basal lamina
Many epithelial cells differ in internal organization
along an axis between the apical surface and the
basal lamina. The apical surface frequently bears
microvilli; less often, it may have cilia or (very rarely)
stereocilia. A single cell typically has only one type
of process; cilia and microvilli are shown together to
highlight their relative proportions. Tight junctions
prevent movement of pathogens or diffusion of
dissolved materials between the cells. Folds of
plasmalemma near the base of the cell increase the
surface area exposed to the basal lamina.
Mitochondria are typically concentrated at the
basolateral region, probably to provide energy for
the cell’s transport activities.
6 Epithelial Tissue Characteristics (cont.)
4) Avascularity
• Do not contain blood vessels
LINING OF RESPIRATORY TRACT
5) Arranged in sheets
• Composed of one or more layers of
cells
6) Regeneration
• Cells are continuously replaced via cell
reproduction
An SEM showing the surface of the epithelium
that lines most of the respiratory tract. The small
bristly areas are microvilli found on the exposed
surfaces of mucus-producing cells that are
scattered among the ciliated epithelial cells.
3 Factors Maintain the Integrity of the Epithelium:
1) Intercellular connections
Epithelial cells are
usually packed
together and
interconnected by
intercellular
attachments.
(See Figure 2.14)
3) Must be replaced
frequently
CAMs
Proteoglycans
(intercellular cement)
Basal Clear layer
lamina Dense layer
2) Attachment of cell membrane to basal lamina:
At their basal surfaces, epithelia are attached
to a basal lamina that forms the boundary
between the epithelial cells and the
underlying connective tissue.
Plasmalemma
Connective tissue
A lamina is a surface or sheet
REVIEW
3 Factors Maintain the Integrity of the
epithelium:
1) Intercellular Connections between cells:
• Holds the cells together
• Prevents the passage of chemicals
and pathogens
• Examples: Cell junctions, CAMs,
intercellular cement gives the
epithelium strength and stability
Epithelial cells are
usually packed
together and
interconnected by
intercellular
attachments.
(See Figure 2.14)
3 Factors Maintain the Integrity of the
epithelium:
2) Attachment of plasmalemma to the basal
lamina:
• The BASAL LAMINA consists of
typically two layers
• Clear layer (superficial)
• Dense layer (contains bundles
of coarse protein fibers; strong)
• Basal lamina in turn attaches to
underlying connective tissue
A lamina is a surface or sheet
3) Replacement frequency
Must be replaced frequently
• Due to exposure to:
• Disruptive enzymes
• Toxic chemicals
• Pathogens
• Mechanical abrasion
• Replaced through time via continual
division of stem cells
• Terminology
• 9 Types of Epithelial Cells
• Simple Squamous
• Stratified Squamous
• Simple Cuboidal
• Stratified Cuboidal
• Simple Columnar
• Stratified Columnar
• Pseudostratified Ciliated
Columnar
• Transitional
• Glandular
• Simple
• Single layer
• Found in protected areas such as the
internal compartments of the body
• Example: lining of alveoli
• Stratified
• Many layers
• Found in areas where there are
mechanical or chemical stresses
• Example: lining of skin
• Transitional
• Changes from simple to stratified
• Example: lining of urinary bladder
• Glandular
• Secretes substances
• Example: goblet cells of the respiratory
tract secrete mucus.
Simple Squamous Epithelium
Locations: Mesothelia lining ventral body cavities;
Endothelia lining heart and blood vessels;
Portions of kidney tubules (thin
sections of nephron
loops); inner lining of
cornea; alveoli of lungs
Functions: reduces friction,
Controls vessel permeability;
Absorption and secretion
Connective
tissue
Cytoplasm
Nucleus
LM  238
Lining of peritoneal
cavity
A superficial view of the simple squamous epithelium
(mesothelium) that lines the peritoneal cavity
Stratified Squamous Epithelium
Functions: Provides physical protection
against abrasion, pathogens, and
chemical attack.
Locations: Surface of skin, lining
Of oral cavity, throat, esophagus,
Rectum, anus, vagina
Squamous
superficial
cells
Stem cells
Basal lamina
Surface of tongue
Connective
tissue
LM  310
Sectional views of the stratified squamous epithelium that covers
the tongue
2 Types of Stratified Squamous Epithelia
1) Non-keratinizing stratified squamous epithelia
1) No dead layers of cells
2) Makes up the lining of the oral
cavity, anal canal, vaginal canal
2) Keratinizing stratified squamous
epithelia
1) Dead layers of cells present
2) Makes up the epidermis of skin
Simple Cuboidal Epithelium
Locations: glands; ducts;
portions of kidney tubules;
thyroid gland
Kidney tubule
Functions: limited protection, secretion
and absorption
Nucleus
Cuboidal
cells
Basal
lamina
A section through the simple cuboidal epithelium lining
A kidney tubule.
Connective
tissue
LM  1400
Stratified Cuboidal Epithelium
Locations: lining of some ducts
(rare)
Sweat gland duct
Functions: protection, secretion,
absorption
Lumen of duct
Stratified
cuboidal cells
Basal lamina
Nucleus
Connective tissue
LM  1413
A sectional view of the stratified cuboidal epithelium lining a sweat gland duct in the skin.
Simple Columnar Epithelium
Locations: Lining of stomach, intestine,
gall bladder, uterine tubes, and collecting ducts
of kidneys
Functions: protection, secretion, absorption
Microvilli
Cytoplasm
Nucleus
Basal lamina
Intestinal lining
a
Loose connective
tissue
LM  350
A light micrograph (x350); note that the cells are shaped like columns. Note the locations
of the nuclei.
Stratified Columnar Epithelium Locations: small areas of the pharynx,
epiglottis, anus, mammary gland, salivary
gland ducts, urethra
Salivary gland duct
Functions: protection
Loose connective
tissue
Deeper basal
cells
Lumen
Superficial
columnar cells
Lumen
Cytoplasm
Nuclei
Basal lamina
LM  175
b
Stratified columnar epithelium is sometimes found along large ducts, such as this salivary gland
duct. Note the overall height of the epithelium and the location and orientation of the nuclei.
Pseudostratified Ciliated Columnar Epithelium
LOCATIONS: Lining of
nasal cavity, trachea, and
bronchi; portions of male
reproductive tract
FUNCTIONS:
Protection;
secretion
Trachea
LM × 350
Cilia
Cytoplasm
Nuclei
Basal lamina
Loose connective
tissue
Pseudostratified ciliated columnar epithelium of the respiratory tract.
Note the uneven layering of the nuclei.
Transitional Epithelium
LOCATIONS: Urinary
bladder; renal pelvis;
ureters
FUNCTIONS: Permits
expansion and recoil
after stretching
Relaxed bladder
Epithelium
(relaxed)
Basal lamina
Stretched bladder
Connective tissue and
smooth muscle layers
LM × 450
Epithelium
(stretched)
Basal lamina
LM × 450
b
Connective tissue and
smooth muscle layers
The cells from an empty bladder are in the relaxed state, while those lining a full urinary bladder
show the effects of stretching on the arrangement of cells in the epithelium.
Glandular Epithelium
• Ducts carry products of exocrine glands to epithelial surface
• Include the following diverse glands
• Mucus-secreting glands
• Sweat and oil glands
• Salivary glands
• Liver and pancreas
• Mammary glands
• May be: unicellular or multicellular
Unicellular Exocrine Glands
(The Goblet Cell)
• Goblet cells produce mucin
• Mucin + water  mucus
• Protects and lubricates many
internal body surfaces
Multicellular Exocrine Glands
• Classified by structure (branching &
shape) of duct
• Can also be classified by mode or type of
secretion
• Merocrine secretion – secretory vesicles
released via exocytosis (saliviary glands)
• Apocrine secretion – apical portion of the
cell is lost, cytoplasm + secretory product
(mammary glands)
• Holocrine secretion – entire cell is
destroyed during secretion (sebaceous
gland)
May also be classified by types of secretions from
exocrine glands
• Serous
• mostly water but also contains some enzymes
• Ex. parotid glands, pancreas
• Mucous
• mucus secretions
• Ex. sublingual glands, goblet cells
• Mixes
• serous & mucus combined
• Ex. submandibular gland
Connective Tissues
Connective Tissue
• Most diverse and abundant tissue
• THREE Main classes
1) Connective tissue proper
2) Blood – Fluid connective tissue
3) Supporting connective tissues
• Cartilage
• Bone tissue
• Components of connective tissue:
• Cells (varies according to tissue)
• Matrix
• Protein fibers (varies according to tissue)
• Ground substance (varies according to tissue)
• Common embryonic origin – mesenchyme
• Functions of Connective Tissue
• Establishing the structural framework of the body
• Transporting fluid and dissolved materials
• Protecting organs
• Supporting, surrounding, and connecting other tissues
• Storing energy
• Defending the body from microorganisms
Classes of Connective Tissue
Connective Tissue Proper - Structures
• Variety of cells, fibers & grounds substances
• depends on use
• Cells found in connective tissue proper:
• Fibroblasts
• Macrophages, lymphocytes (antibody producing cells)
• Adipocytes (fat cells)
• Mast cells
• Stem cells
• Fibers:
• Collagen – very strong & abundant, long & straight
• Elastic – branching fibers with a wavy appearance (when relaxed)
• Reticular – form a network of fibers that form a supportive framework in soft organs (i.e.
Spleen & liver)
• Ground substance:
• Along with fibers, fills the extracellular space
• Ground substance helps determine functionality of tissue
Connective Tissue Proper - Classifications
• Loose Connective Tissue
• Areolar
• Reticular
• Adipose
• Dense Connective Tissue
• Regular
• Irregular
• Elastic
Areolar (loose) Connective Tissue
• Description
• Gel-like matrix with:
• all three fiber types (collagen, reticular, elastic) for
support
• Cells – fibroblasts, macrophages, mast cells, white blood cells
• Highly vascular tissue
• Function
•
•
•
•
Wraps and cushions organs
Holds and conveys tissue fluid
Important role in inflammation
Main battlefield in fight against infection
• Location
• Widely distributed under epithelia
• Packages organs
• Surrounds capillaries
Adipose Tissue
• Description
• Closely packed adipocytes
• Have nucleus pushed to one side by
fat droplet
• Function
• Provides reserve food fuel
• Insulates against heat loss
• Supports and protects organs
• Location
• Under skin
• Around kidneys
• Behind eyeballs, within abdomen and
in breasts
Reticular Connective Tissue
• Description – network of
reticular fibers in loose
ground substance
• Function – form a soft,
internal skeleton (stroma) –
supports other cell types
• Location – lymphoid organs
• Lymph nodes, bone marrow, and
spleen
Dense Irregular Connective Tissue
Description
 Primarily irregularly arranged collagen
fibers
 Some elastic fibers and fibroblasts
Function
 Withstands tension
 Provides structural strength
Location
 Dermis of skin
 Submucosa of digestive tract
 Fibrous capsules of joints and organs
Dense Regular Connective Tissue
Description
 Primarily parallel collagen fibers
 Fibroblasts and some elastic fibers
 Poorly vascularized
Function
 Attaches muscle to bone
 Attaches bone to bone
 Withstands great stress in
one direction
Location
 Tendons and ligaments
 Aponeuroses - collagenous sheets/broad tendons; assist in attaching superficial
muscles to another muscle or structure.
 Fascia – encloses muscles
 Dura mater – encloses brain/spinal cord
Cartilage
• Characteristics:
• Firm, flexible tissue
• Contains no blood vessels or
nerves
• Matrix contains up to 80%
water
• Cell type – chondrocyte
• Types:
• Hyaline
• Elastic
• Fibrocartilage
Cartilages in the body.
Cartilage in
external ear
Cartilages
in nose
Epiglottis
Thyroid cartilage
Larynx
Cricoid cartilage
Trachea
Lung
Articular cartilage
of a joint
Costal
cartilage
Cartilage
in intervertebral
discs
Respiratory
tube cartilages
in neck and thorax
Cartilages
Pubic
symphysis
Articular cartilage
of a joint
Meniscus
(padlike cartilage
in knee joint)
Hyaline cartilages
Elastic cartilages
Fibrocartilages
Hyaline Cartilage
• Description
• Imperceptible collagen fibers (hyaline = glassy)
• Chodroblasts produce matrix
• Chondrocytes lie in lacunae
• Function
• Supports and reinforces
• Resilient cushion
• Resists repetitive stress
• Location
• Ends of long bones
• Costal cartilage of ribs
• Cartilages of nose,
trachea, and larynx Location
Elastic Cartilage
Description
Similar to hyaline cartilage
More elastic fibers in matrix
Function
Maintains shape of structure
Allows great flexibility
Location
Supports external ear
Epiglottis
Fibrocartilage
Description
 Matrix similar, but less firm than
hyaline cartilage
 Thick collagen fibers predominate
Function
 Tensile strength and ability
to absorb compressive
shock
Location
 Intervertebral discs
 Pubic symphysis
 Discs of knee joint
Bone Tissue
• Function
• Supports and protects organs
• Provides levers and
attachment site for muscles
• Stores calcium and other
minerals
• Stores fat
• Marrow is site for blood cell
formation
• Location
• Bones
• Bone cells are called osteocytes
Blood Tissue
Description
 red and white blood cells
in a fluid matrix
Function
 transport of respiratory
gases, nutrients, and wastes
Location
 within blood vessels
Characteristics
 An atypical connective tissue
 Consists of cells surrounded by fluid matrix
Covering and Lining Membranes
• Combine epithelial tissues
and connective tissues
• Cover broad areas within
body
• Consist of epithelial sheet
plus underlying connective
tissue
Types of Membranes
• Cutaneous membrane – skin
• Mucous membrane
• Lines hollow organs that open to surface of body
• An epithelial sheet underlain with layer of lamina propria
• Serous membrane – slippery membranes
• Simple squamous epithelium lying on areolar connective tissue
• Line closed cavities
• Pleural, peritoneal, and pericardial cavities
• Synovial membranes – lining joint cavities
• Loose connective (areolar) + simple squamous epithelium
• Secretes fluid (synovial fluid) which lubricates, protects & cushions joint
structures
Muscle Tissue
• 3 Types
• Skeletal muscle tissue
• Cardiac muscle tissue
• Smooth muscle tissue
Skeletal Muscle Tissue
• Characteristics
• Long, cylindrical cells
• Multinucleate
• Obvious striations
• Function
• Voluntary movement
• Manipulation of
environment
• Facial expression
• Location
• Skeletal muscles attached to bones (occasionally to skin)
Cardiac Muscle Tissue
• Function
• Contracts to propel blood into circulatory system
• Characteristics
• Branching cells
• Uni-nucleate
• Intercalated discs
• Location
• Occurs in walls of heart
Smooth Muscle Tissue
• Characteristics
• Spindle-shaped cells with
central nuclei
• Arranged closely to form
sheets
• No striations
• Function
• Propels substances along
internal passageways
• Involuntary control
• Location
• Mostly walls of hollow organs
Nervous Tissue
Nervous Tissue
• Function
• Transmit electrical signals
from sensory receptors to
effectors
• Location
• Brain, spinal cord, and nerves
• Description
• Main components are brain,
spinal cord, and nerves
• Contains two types of cells
• Neurons – excitatory cells
• Supporting cells (neuroglial cells)
Tissue Response to Injury
• Restoration involves
• Inflammation
• Regeneration (repair)
• Inflammation
• Due to something that damages/kills cells or fibers or in some way
damage tissue, causing . . .
• Swelling
• Warmth
• Redness
• Pain
• These common conditions are a result of mast cell activation –
releases vasodilators such as histamine
Tissue Response to Injury
• Goal:
• Restore normal function to tissue
• Challenges
• Some tissues are non-vascular and will repair very slowly
• If excitable tissue is replaced by scar tissue – function is lost!
The Tissues Throughout Life
• Early on – Gastrulation
• The most important time in your life!!
• This is when tissues differentiate – mess up here and you don’t develop correctly
• At the end of second month of development:
• Primary tissue types have appeared
• Major organs are in place
• Adulthood
• Only a few tissues regenerate
• Many tissues still retain populations of stem cells
• With increasing age:
•
•
•
•
•
Epithelia thin
Collagen decreases
Bones, muscles, and nervous tissue begin to atrophy
Poor nutrition and poor circulation – poor health of tissues
Increased chance of developing cancer