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Tissues
Chapter 4
Body Cells and Fluids
Human body is multicellular….made of trillions of cells.
Cells differentiate-change from unspecialized to specialized cells
Each cell has unique structure and unique function.
Cytology: study of cells.
Body has a lot of fluid:
Intracellular fluid/cytoplasm: fluid inside the cells.
Extracellular fluid/tissue fluid/interstitial fluid/
intercellular fluid: fluid outside the cells.
Homeostasis is maintained by maintaining the fluids in different
compartments.
Tissues
In the body, cells are grouped together.
Tissues: refers to a group of cells that have similar
structure and functions.
Histology: study of tissues.
Biopsy: taking a sample from a patient  histology to
diagnose diseases.
Autopsy: taking samples from a dead person  to
determine the cause of death.
Cell Junctions
Most body cells stay anchored to their
location and to their neighboring cells.
How do cells attach?
Intercellular junctions: complex proteins that
provide contact between the cells.
Tight
junction
Gap junctions
Desmosome
1) Tight junctions: proteins that zip two cells
tightly.
No spaces between the cells.
Nothing can pass between the cells.
Found between epithelial cells lining the
intestine.
2) Desmosomes: Form an adhesive bond
between cells-at a localized region
Resist stretching and twisting as in skin and heart
muscles.
3) Gap junctions: protein channels that
physically and chemically connect adjacent cells.
Cardiac muscle tissue  coordinate
heart beating.
Types of Tissues
There are four types of tissues that make up human
body:
Epithelial tissue –consist of epithelia and glands
-covers exposed external and internal surfaces, lines
body cavities
Connective tissue – provides protection and support to
the body.
Muscle tissue – allows the movement of the body or
body parts, and generates heat.
Neural tissue – detects changes in external and internal
environment, and allows body to respond to the
changes in order to maintain homeostasis
Epithelial Tissue
Location of epithelial tissue:
Epithelial tissue covers/lines most body surfaces –
Outer surface of the body…skin.
Lining body openings…nasal, anus, mouth,
reproductive, urinary.
Inner lining of organs…brain, heart, stomach, bladder.
Lining body cavities…thoracic, abdominal, joints.
Epithelial tissue forms glands that secrete fluids or
hormones:
Salivary glands, oil glands, sweat glands, thyroid.
Epithelial Tissue
Major characteristics of epithelial tissue:
Apical
surface
A. Cellularity-Epithelial cells are tightly
packed…connected by desmosomes and
tight junctions…with no intercellular
spaces.
B. Since epithelial tissue is a surface
tissue, the cells have polarity:
Basal
surfaces
Apical surface – free surface that is
exposed to the body cavity/surface.
Basal surface – attached to the tissues
underneath with the help of basement
membrane that is secreted by the
epithelial cells.
C. Epithelial tissue is avascular…blood vessels do not penetrate the
tissue…exchange of nutrients and waste products with blood vessels is by
diffusion.
D. Repair & Regeneration-Epithelial cells have a high capacity to divide (mitosis) to
form new cells and replace damaged cells.
Epithelial Tissue
Functions of epithelial tissue:
A. Protection – from wear and tear, infections, chemical
damage, dehydration.
B. Controls permeability – being a surface tissue,
chemicals have to cross it in order to enter or exit
the body; secretion, absorption of chemicals;
passage can be very selective due to the presence
of specific transport proteins present in their cell
membranes.
C. Sensation –nerve endings or specialized
cells associated with the tissue give sensation to
make body aware of its internal/external
environment.
D. Produce secretions-Epithelial cells that produce
secretions are gland cells
Epithelial Tissue
Simple
Stratified
Classification of epithelial tissue:
A. Based on the number of layers of cells
Simple epithelium: one layer of cells.
Stratified epithelium: 2 or more layers of cells.
Pseudostratified epithelium: looks multilayered but in actuality is one
layer.
B. Based on cell shape
Squamous epithelium: flat, tile like cells.
Cuboidal epithelium: cube/dice like cells.
Columnar epithelium: tall/column like cells.
Transitional epithelium: cell shape changes depending on the status of the
organ.
Epithelial tissue
Simple Squamous Epithelium
Simple squamous epithelium: one layer of flat cells.
Location: Found lining pleural, pericardial and peritoneal cavities, lining heart
and blood vessels (endothelium), alveoli (air sacs) exchange surface in lungs.
Function: filtration, absorption, secretion.
Epithelial Tissues
Examples of epithelial tissue:
Simple Cuboidal Epithelium
Nucleus
Cuboidal
cells
Simple cuboidal epithelium: one layer of cube-shaped cells.
Location: Found in kidneys, thyroid gland
Function: absorption, secretion.
Epithelial Tissue
Examples of epithelial tissue:
Simple Columnar Epithelium
Microvilli
Cytoplasm
Nucleus
Simple columnar epithelium: one layer of tall/column-like cells.
Notice small folds of the plasma membrane called microvilli that increase
the surface area.
Location: Found lining stomach and intestines.
Function: absorption, secretion.
Epithelial tissue
Stratified Squamous Epithelium
Stratified squamous epithelium: 2 or more layers of flat cells.
For shape of the cells, look at the cells in the top layers of the tissue. Bottom layer of cells are
usually dividing stem cells and will be cuboidal!
Location: Found lining areas subject to abrasion-outer surface of the skin, inner surface of the
oral cavity, pharynx, esophagus, anus, vagina.
Function: provides protection against wear and tear, infections and chemicals.
Epithelial Tissue
Examples of epithelial tissue:
Stratified Cuboidal Epithelium
Stratified cuboidal epithelium: 2 or more layers of cube-shaped cells.
Again, for shape of the cells, look at the cells in the top layers of the tissue. Bottom layer of
cells are usually dividing stem cells and will be cuboidal!
Location: Rare but found in sweat glands.
Function: contributes to secretion, conducting.
Epithelial Tissue
Examples of epithelial tissue:
Ciliated Pseudostratified Columnar Epithelium
Cilia
Cytoplasm
Nuclei
Ciliated pseudostratified columnar epithelium: looks multilayered but in actuality it
is one layer of tall/column-like cells.
Notice small hair like structures called cilia that move substances on the surface of the cells.
Some swollen cells called Goblet cells may also be associated with this epithelium 
secrete mucus.
Location: Found lining trachea – the windpipe.
Function: filter air by trapping dust particles and microbes, move mucus.
Epithelial Tissue
Examples of epithelial tissue:
Stratified Transitional Epithelium
Stratified transitional epithelium: many layers of cells; cell shape depends on
the status of the organ.
Location: Found lining the urinary bladder.
Function: allow stretching and relaxing of the organ and protect from acidic
urine.
Epithelial Tissue
Glandular epithelium
Epithelium also forms glands.
Glands: structures that secrete something – fluids, oils, hormones.
There are two types of glands:
Exocrine glands:
1) Secretions are released onto a
surface ….internal/external epithelial
surface.
Secretions: mucus, sweat, oil, wax,
digestive enzymes.
2)Secrete products through a
duct/tube.
3) Examples: sweat glands, salivary
glands, mammary glands, pancreas.
Endocrine glands:
1) Secretions directly diffuse into blood
….do not come out on the surface.
Secretions: hormones.
2) Ductless.
3) Examples: pituitary, adrenal, thyroid
glands, pancreas.
Epithelial Tissue
Structural classification of exocrine glands
Tracheal lining
Small & large
intestine
Goblet cells
A. Unicellular glands – single cell-Goblet cell  secrete mucus.
Location1) Pseudostratified ciliated columnar epithelia of trachea
2) Simple columnar epithelia of small/large intestine
B. Multicellular glands – composed of many cells…most glands.
Sweat glands  secrete sweat.
Sebaceous glands  secrete sebum.
Salivary glands  secrete saliva.
Epithelial Tissue
Functional classification of exocrine glands
Merocrine
Vesicles released by exocytosis
Glandular cell is intact
Eg:-sweat, salivary gland
Apocrine
Apical Cytoplasm breaks off from
the cell with secretory vesicles
Eg:-mammary gland
Holocrine
-Gland cells packed with secretory
vesicles and then burst
- Gland cell is destroyed
- Eg:-sebaceous gland (sebum)
Connective Tissue
Location of connective tissue:
Connective tissue is not a surface tissue.
It is distributed all over the body.
Examples of connective tissue:
1) Bones
2) Blood
3) Fat tissue
4) Tissue that fills spaces in the organs
5) Tissue that connects skin to the muscles underneath
6) Cartilage that makes up earlobe and tip of the nose
7) Ligament-Tissue that connects bones in the joints
8) Tendon-Tissue that attaches muscles to the bones
Connective Tissue
Cells
Fibers
Ground
substance
Major characteristics of connective tissue:
A. Specialized cells are dispersed…with lots of intercellular spaces.
B. Intercellular space is filled with fibers and ground substance that together
make up matrix- can be fluid, gelatinous, fibrous, calcified solid material or a
combination of fibers and fluid.
C. Most have extensive blood vessel and nerve supply.
Connective Tissue
Functions of connective tissue:
A. Protects – bones protect organs (brain, heart, lungs),
capsule protects organs (kidneys), WBCs protect from
infections.
B. Connects – tendons connect muscles to bones,
ligaments connect bones to bones, mesenteries connect
intestines.
C. Stores – adipose tissue stores fats, bones store calcium.
D. Transports – blood transports nutrients, gases,
hormones, wastes.
E. Movements – bones and cartilage help muscles in
movement of the body and body parts.
Connective Tissue
Cells
Fibers
Ground
substance
Structure of connective tissue:
Connective tissue is composed of:
Cells that are dispersed…with lots of intercellular spaces.
Intercellular space is filled with matrix…non-living material.
Connective Tissue
Cells
Fibers
Ground
substance
Connective tissue Cells:
Root terminology:
Blasts – cells that
create other cells.
Cytes – cells that
maintain.
Clasts – cells that
break down matrix
or cells.
A. Fibroblasts – most common type of cell  form fibrocytes.
B. Fibrocytes – derived from fibroblasts  maintain connective tissue fibers.
C. White blood cells (WBC) – protect against infections and help repair damaged tissue.
D. Other specialized cells – adipocytes (fat cells), chondrocytes (cartilage cells), osteocytes
(bone cells), erythrocytes-leukocytes-thrombocytes (blood cells).
Connective Tissue
Cells
Fibers
Ground
substance
Connective tissue
Matrix:
Refers to non-living
material present in the
spaces between the
dispersed cells.
Composed of fibers and
ground substances.
A. Protein Fibers – Made by fibroblasts and maintained by fibrocytes.
Provide strength and support.
1) Collagen fibers – linear, most abundant fibers in bone, tendons and ligaments.
2) Reticular fibers – branched, form stroma (spaces) of many soft organs like liver.
3) Elastic fibers – made of coiled elastin, found in skin, blood vessels and lungs.
B. Ground substance – fills spaces between the fibers.
Semi-solid in cartilage, solid in bones, liquid in blood/lymph.
Connective Tissue
Classification of connective tissue:
Remember, all connective tissues have dispersed cells with intercellular matrix.
Connective tissues are divided into 3 major types:
I. Connective tissue proper- has many types of cells and matrix that is composed of
network of fibers and fluid ground substance.
II. Fluid connective tissue- has unique cells suspended in liquid matrix…no fibers.
III. Supporting connective tissue- has fewer types of cells with matrix that is made of
dense network of fibers and gelatinous or solid ground substance.
Cells
Fibers
Ground
substance
Connective Tissue
I. Connective tissue proper-Cells and Matrix (fibers & fluid ground substance)
A. Embryonic connective tissue- found in the developing embryo.
Has scattered mesenchymal cells with network of collagenous fibers and
gelatinous ground material.
Two types:
Mesenchyme- first type of connective tissue to differentiate in a 3-4 week
embryo  forms all other types of connective tissues by 8 weeks.
Mucous connective tissue/Wharton’s jelly- present in umbilical cord –
supports blood vessels traveling between mother and fetus.
Mesenchymal
Cells
Fibers
Connective Tissue
I. Connective tissue proper-Cells and Matrix (fibers & fluid ground substance)
B. Loose connective tissue- composed of loosely packed fibers (collagen, reticular,
elastic) with dispersed fibroblasts and WBCs.
Fills spaces in organs, surrounds blood vessels and nerves, attaches epithelial
tissue to other tissues.
i) Areolar connective tissue- widely distributed in the body:
Subcutaneous layer that connects skin to the muscles underneath.
Mesenteries that connects intestines together.
Fibroblasts
WBC
Fibers
Connective Tissue
I. Connective tissue proper-Cells and Matrix (fibers & fluid ground substance)
B. Loose connective tissue- composed of loosely packed fibers (collagen, reticular,
elastic) with dispersed fibroblasts and WBCs.
i) Areolar connective tissue
ii) Adipose tissue- fat tissue composed of adipocytes (fat cells) that store fat…cells
can expand with increase in fat storage.
Provides insulation and protection for certain organs, source of energy and heat.
Found under the skin of the flanks, gluteal region, breast etc..
Adipocytes
Connective Tissue
I. Connective tissue proper-Cells and Matrix (fibers & fluid ground substance)
B. Loose connective tissue- composed of loosely packed fibers (collagen, reticular,
elastic) with dispersed fibroblasts and WBCs.
i) Areolar connective tissue
ii) Adipose tissue
iii) Reticular connective tissue- has a lot of reticular fibers and forms a framework
(stroma) to hold cells together in liver, spleen and bone marrow.
Reticular
fibers
Connective Tissue
I. Connective tissue proper-Cells and Matrix (fibers & fluid ground substance)
C. Dense connective tissue- composed of densely packed fibers with dispersed
fibroblasts  gives strength.
i) Dense regular connective tissue- collagen fibers are all oriented in same direction
…appear like a strong rope.
Have limited blood supply  slower repair of injuries.
Tendons: strong attachment of muscles to the bones.
Ligaments: strong attachment of bones to the bones at the joint.
Fibroblasts
Fibers
Connective Tissue
I. Connective tissue proper-Cells and Matrix (fibers & fluid ground substance)
C. Dense connective tissue- composed of densely packed fibers with dispersed
fibroblasts  gives strength.
i) Dense regular connective tissue
ii) Dense irregular connective tissue- collagen fibers are irregularly arranged…like a
network.
Vocal cords: in larynx for sound production.
Capsules: jacket around certain organs…kidneys, testes.
Fibers
Connective Tissue
Classification of connective tissue:
I. Connective tissue proper
II. Fluid connective tissue- has unique cells suspended in liquid matrix….no fibers.
Examples: blood, lymph.
Blood is composed of:
Erythrocytes (RBC) – transports gases (O2, CO2).
Leukocytes (WBC) – protect against infections.
Thrombocytes (platelets) – facilitate blood clotting.
Lymph is composed of fluid and WBC.
Erythrocytes
(RBC)
Leukocytes
(WBC)
Thrombocytes
(platelets)
Connective Tissue
Classification of connective tissue:
III. Supporting connective tissue- has fewer types of cells with matrix that has denser
network of fibers with gelatinous/solid ground substance.
Provides protection and supports softer tissues and organs.
A. Cartilage: has collagenous and elastic fibers with jelly-like ground substance
called chondroitin sulfate.
Chondrocytes – cartilage cells are located in spaces called lacuna.
Has no blood vessels or nerves….cells are nourished by diffusion….slow growth
and repair.
Depending on the type and ratio of fibers and matrix, cartilage can be:
Hyaline cartilage – sternum, part of ribcage, covers ends of long bones, in tracheal wall.
Fibrocartilage – makes up vertebral discs, pads in knee joint.
Elastic cartilage – found in external earlobe.
Hyaline
Fibro
Elastic
Chondrocyte
Lacuna
Matrix
Connective Tissue
Classification of connective tissue:
III. Supporting connective tissue
B. Bone (osseous) tissue: Osteon-Basic functional unit of a mature bone.
Has collagenous fibers with solid ground substance made of Ca salt (mostly calcium
phosphate, some calcium carbonate).
Central (Haversian) canal tiny tubes with a containing blood vessels and nerves.
Osteocytes – mature bone cells that are dispersed in solid matrix.
Canaliculi: tiny canals that connect central canal with lacuna for nutrients.
Lamellae: concentric circles of matrix around the central canal.
Lacunae with osteocytes: dispersed among the lamellae.
Osteon
Lamellae
Lacuna
with
Osteocyte
Central
canal
Muscle Tissue
Location of muscle tissue:
Muscle tissue makes up the large muscles that are
attached to the bones.
Muscle tissue makes up the heart.
Muscle tissue is also present in the wall of the visceral
organs such as stomach, intestines, urinary bladder,
blood vessels.
Muscle Tissue
Major characteristics of muscle tissue:
A. Muscle tissue is composed of cells
called muscle fibers.
B. Muscle fibers (cells) can contract and
relax.
C. When muscle fibers contract  they
generate heat.
Muscle Tissue
Functions of muscle tissue:
A. Movement – help in the movement of the body
and body parts.
B. Posture – helps in maintaining body posture.
C. Thermoregulation – when muscle fibers contract
 heat is generated  main source of heat for
body to maintain temperature.
D. Blood circulation- Cardiac muscles in the heart
E. Elasticity, Contractility & Support-Muscles in the
wall of visceral organs
3 types of muscle tissue:
1) Skeletal muscle tissue
2) Cardiac muscle tissue
3) Smooth muscle tissue
Muscle Tissue
1) Skeletal muscle tissue:
Location – makes up large muscles attached to the skeleton.
Muscle fibers – long, huge fibers.
Fibers are multinucleated.
Fibers are striated…have a uniform banding pattern.
Action – voluntary.
Skeletal muscle-Striated voluntary muscle
Striations
Nuclei
Muscle
fiber
Muscle Tissue
2) Cardiac muscle tissue:
Location – makes up the wall of the heart.
Consist of a branching network of interconnected cardiac muscle cell
(cardiocyte)
Transverse thickenings (intercalated disc)…help in communication.
Fibers are uninucleated.
Fibers are striated…have a uniform banding pattern.
Action – involuntary.
Cardiac muscle-Striated involuntary muscle
Nuclei
b
Cardiac
muscle
cells
Intercalated
discs
Striations
Muscle Tissue
3) Smooth muscle tissue:
Location – found in the wall of visceral organs.
Muscle fibers – spindle-shaped fibers.
Fibers are uninucleated.
No striation.
Action – involuntary.
Smooth Muscle Tissue- Nonstriated involuntary muscle
Nuclei
Smooth
muscle
cells
LM × 235
Neural Tissue
Location of nervous/neural tissue:
Nervous tissue makes up brain, spinal cord and nerves.
Functions of nervous/neural tissue:
It senses changes in external and internal environment.
It generates impulses that travel along the nerves.
It integrates information.
It helps the body respond to the changes and maintain
homeostasis.
Neural Tissue
Nuclei of neuroglia
Composition of nervous
tissue:
Cell body
Axon
Nucleolus
Nucleus
of neuron
Dendrites
LM ×
600
Nerve processes
Cell body
A representative neuron
(sizes and shapes vary widely)
Neurons –
Cells that generate and
conduct impulses.
They are made of cell body
with nucleus, cytoplasm
and other cellular
organelles.
Cell body has nerve
extensions/processes
help conduct impulses.
Neuroglial cells –
Glial cells that protect and
support neurons.
Review: Types of Tissues
Epithelial tissue –
Covers and lines outer and inner body surfaces.
Lines inner body cavities.
Forms glands.
Connective tissue –
It is the most abundant tissue in the body.
It provides protection and support to the body.
It connects tissues or parts of the body.
Muscle tissue –
It is made of muscle fibers (cells).
It helps with the movement of the body or body parts.
It generates heat and helps with temperature regulation.
Nervous/neural tissue –
It detects changes in external and internal environment.
It allows body to respond to the changes in order to
maintain homeostasis.
Membranes
Membranes:
Refers to sheaths that cover and lines outer and
inner body surfaces, organs and cavities.
Membranes protect surfaces and organs, and
secrete fluid.
Membranes
Mucous membranes
(mucosa)-Line
passageways that
open to outside of the
body. Secrete mucus.
Eg. digestive, urinary,
respiratory, and
reproductive tracts.
Serous membranes
(serosa)-Line body
cavities that do not open
to the outside.
Peritoneal - abdominal
Pleural – around the lung
Pericardial – around heart
Cutaneous
membrane, or skin,
covers the outer
surface of the body.
Synovial membranes
line joint cavities and
produce synovial
fluid within the joint.
Consists of epithelial
tissue and a thin
layer of connective
tissue. Secrete
mucus-Reduce
friction and facilitate
absorption &
secretion
Consists of epithelial
tissue and a thicker
layer of connective
tissue.
Parietal and Visceral.
Secretes serous fluid
 lubricated the
organs.
Consists of stratified
squamous epithelial
layer (epidermis) that
is attached to
connective tissue
layer (dermis).
Consists of just
connective tissue.
No epithelium.
Blood vessels
secrete synovial fluid
to lubricate and
nourish the joint.
Tissue Repair
What happens when a tissue gets damaged?
Inflammation/Inflammatory process: a process initiated by the body to
prevent infections and clean up damaged cells.
Necrosis: refers to premature death of the damaged cells, that is not due to
normal aging process.
Regeneration: a repair process that will allows the body to resume its
functions.
Fibrosis: when normal tissue is replaced by fibrous connective tissue.
Often seen in deep skin damage, muscle tissue damage, lung infections.