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Chapter 5 Tissues
5.1 Introduction
• Cells are the basic unit of structure and function
in the humans.
• Cells are then organized into groups called
tissues.
– Tissues are composed of similar cells specialized to
carry out a particular function.
• In humans there are 4 major types of tissue:
– Epithelial – protective coverings
• Function – secretion and absorption
– Connective – support soft body parts and binds
structures together
– Muscle – produce and control body movement
– Nervous – conduct impulses that control and
coordinate body activity
Epithelial Tissues
• Found throughout the body
• Covers organs, forms inner lining of body
cavity, lines hollow organs (stomach)
• Always has a free (apical) surface exposed to the
outside or internally to an open space.
• The underside is attached or anchored to
connective tissue by the basement membrane.
– Basement membrane- a thin nonliving layer
• Do not contain blood vessels
– Underlying connective tissues are very abundant with
blood vessels
• **This is why you only bleed if you get a deep cut**
• Divide often
– Allows cuts to heal quickly
• Tightly packed
– Makes them effective coverings
• Other functions: secretion, absorption, and
excretion
• Classified based on their shape:
– Squamous- flattened
– Cuboidal – cube shaped
– Columnar – elongated, tall
– Stratified- 2 or more layers
– Simple – single layer
Simple Squamous Epithelium
• Single layer of thin flattened
cells
• Fit tightly (like tiles)
• Nuclei are broad and thin (in
depth)
• Substances easily pass
through this layer
– Common sights of diffusion
and filtration
• Ex.) alveoli in lungs (exchange
O2 and CO2)
– They are easily damaged
because they are so thin
Simple Cuboidal Epithelium
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Single layer of cube shaped cells
Centrally located spherical nuclei
Not tightly packed
Covers ovaries and most of the
kidneys
Free side faces the lumen (hollow
channel)
Function
In kidneys: secretion and
absorption
In glands: secrets glandular
products
Simple Columnar Epithelium
• Elongated (longer than wide)
• Single layer of cells
• Elongated nuclei; found close to the basement
membrane
• Can be ciliated
– In female reproductive tract cilia aides in movement of
the egg through the uterine tube to the uterus
• Nonciliated simple columnar epithelium lines
uterus and parts of the digestive tract (stomach and
large intestines)
• Because of the elongation,
tissue is thick (protects
underlying tissue)
• Secrets digestive fluids and
absorb nutrients
• Goblet cells are found
among the cells
– They secrete a protective
fluid called mucus onto the
free surface of the tissue.
Pseudostratified Columnar Epithelium
• Appear to be stratified but actually aren’t
• Nuclei are at 2 or more levels in a row of
aligned cells.
• Vary in shape
• All reach the basement membrane, but not all
each the free surface
• Common for them to have cilia on the free
surface
• Goblet cells secret mucus which the cilia then
moves away
– Line respiratory system – trap dust or other particles
and sweep it away
Stratified squamous epithelium
• Many layered; very thick
• Cells divide in deep layers and new ones push
the older farther outward where they are
flattened
• Named for the shape of the top layer of cells
• Form outer layer of skin (epidermis)
• As skin cells age they accumulate keratin (a
protein) then harden and die
• Keratinization – produces a
covering of dry tough,
protective material that
prevents water and other
substances from escaping
underlying tissues.
– Also blocks microorganisms and
other chemicals from entering
• Lines the oral cavity,
esophagus, vagina and anal
canal
– **do NOT keratinize: they stay
soft, moist, and all cells on it’s
free surfaces stay alive**
Stratified Cuboidal Epithelium
• 2 or more layers of
cuboidal cells
• Provide protection
• Line larger ducts (lumen)
in mammary glands, sweat
glands, salivary glands and
pancreas
• Lining of developing
ovarian follicles and
seminiferous tubules (parts
of the female and male
reproductive system)
Stratified Columnar Epithelium
• Several layers of cells
• Superficial cells of
consist of columnar cells
• Basal layers consist of
cuboidal
• Found in male urethra
and ductus deferens and
the pharynx
Transitional epithelium
• Specialized to change in response to increased
tension
• Forms inner lining of urinary bladder and lines the
ureters and superior urethra
• When the walls of one of the organs contracts the
tissue consists of several layers of cuboidal cells;
when the organ distends tissue stretches and
physical relationship among the cells changes
– ***expandable lining***
• Forms barrier that helps
prevent the contents of
the urinary tract from
diffusing back into the
internal environment.
Glandular Epithelium
• Cells specialized to produce and secrete
substances into ducts or into body fluids
• Secrete products into ducts that open onto
surfaces -> exocrine glands
– Ex.) skin; digestive tract
• Endocrine glands- secrete their products into
tissue fluid or blood
Exocrine Glands
• Classified according to the ways they secrete
their products
– 1. merocrine glands – release fluids by exocytosis
• Ex.) salivary, pancreatic and sweat glands
• Apocrine glands
– Loose small parts of their glandular bodies during
secretion
• Ex.) mammary glands, ceruminous lining inner ear canal
• Holocrine glands
– Disintegrate entire cell, fills with secretory product
• Ex.) sebaceous gland (The sebaceous glands are microscopic
exocrine glands in the skin that secrete an oily or waxy matter,
called sebum, to lubricate and waterproof the skin and hair of
mammals.)
• Most exocrine glands are merocrine
• Merocrine can be classified by the mucus or serious
fluid they secrete
– 1. serous fluid- watery and high in enzymes
• Lubricants
– 2. Mucus- thicker fluid, rich in glycoproteins (mucin)
• Protection in digestive, respiratory and reproductive systems
• *mucus and goblet cells secrete mucus in different
parts of the body*
5.3 Connective Tissue
• General characteristics
– Bind structures
– Provide support
– Serve as frame works
– Fill spaces
– Store fat
– Produce red blood cells
– Protect against infections
– Help repair tissue damage
– are spaced further apart than epithelium cells
– Contain extracellular matrix between them
• Extracellular matrix- molecules that fill spaces between
cells; consisting mostly of protein fiber networks
– Consistency of extracellular matrix varies from fluid
to semisolid to solid
– Most an divide
– Varying degrees of vascularity; most have good
blood supply
Major Cell Types
• Contain a varitey of cell types
– 1. fixed- reside in tissue for long time (fibroblasts
and mast cells)
– 2. wandering – move and appear temporally often in
response to a wound or infection (macrophages)
Fibroblasts
• Most common type of connective tissue
• Produce fibers by secreting proteins into the
extracellular matrix of connective tissue
Macrophages
• Also known as histiocytes
• Originate from white blood
cells
• Almost as numerous as
fibroblasts in connective
tissue
• Specialized to carry out
phagocytosis
• Can move about
• Function as
scavenger/defense cells that
clear foreign particles from
tissues
Mast Cells
• Large and widely
distributed
• Found near blood cells
• Release heparin (prevents
blood clotting)
• Release histamine (assoc.
with inflammation and
allergies)
Connective Tissue Fibers
• Fibroblasts produce 3 types:
– 1. collagenous
– 2. elastic
– 3. reticular
Most abundant
Collagenous fibers
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Thick threads of protein (collagen)
Grouped in long, parallel bundles
Flexible but only slightly elastic
Have great tensile strength (resist pulling force)
Important in holding structures together like:
– Ligaments – bone to bone
– Tendons – muscle to bone
• Tissue with lots of
collagenous fibers are
dense connective tissue
• Often appear white
(white fibers)
• Loose connective tissues have
few collagenous fibers
(compared to dense
connective tissue)
Elastic Fibers
• made of elastin
– Elastin is a spring like protein
• Form complex network (they branch)
• Weaker than collagenous fibers, easily stretched
and deformed
– Will return to original shape with the force is
removed
• Common in body parts subject to normal
stretching (vocal chords)
Reticular Fibers
• Thin collagenous fibers
• Highly branched
• Form delicate support
Categories of Connective tissue
• 2 major categories
– 1. connective tissue proper
• Loose and connective tissue
– 2. Specialized connective tissue
• Cartilage, bone and blood**
– Blood is considered a connective tissue because it has a
matrix. The living cell types are red blood cells, also called
erythrocytes, and white blood cells, also called leukocytes . The
fluid portion of whole blood, its matrix, is commonly called
plasma.
Loose connective tissue
• Includes areolar, adipose and reticular connective
tissue
• 1.) areolar tissue- forms delicate, thin membranes
throughout the body
– Made mostly of fibroblasts
– Cells are spaced far apart
– Separated by a gel-like ground substance that contains
many collagenous and elastic fibers that fibroblast secret.
– Binds skin to underlying organs and fills space between
muscles
– Lies beneath most layers of epithelium
• 2.) adipose tissue (fat)
– Develops when certain cells (adipocytes) store fat as droplets in
their cytoplasm and enlarge
– When cells become so abundance they crowd other cell types and
form adipose tissue
– Lies beneath the skin, and is also found:
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Between muscles
Around kidneys
Behind eyes
In some abdominal membranes
On the surface of the heart
Around joints
– Cushions joints and some organs such as the kidneys
– Insulates beneath the skin and stores energy in fat molecules
• 3.) Reticular connective tissue
– Composed of thin, collagenous fibers in a 3D
network
– Provides framework for internal organs
• Ex.) liver and spleen
Dense Connective Tissue
• Consists of many closely packed, thick
collagenous fibers with a network of elastic
fibers (mostly fibroblasts)
• Very strong – allows for high pulling force
• Binds with body parts as tendons and ligaments
• Also in protective white layer of the eye and
deep skin layer
• Blood supply is poor; slowing healing
Cartilage
• Ridged connective tissue
• Provides support, framework and attachments,
protects underlying tissue
• Forms structural models for many developing
bones
• Extracellular matrix is abundant and composed
of collagenous fibers
• Cartilage cells are called chondrocytes.
– Covered in a connective tissue called perichondrium
• Where nutrients diffuse through them to the cartilage
• Heals very slowly and chondrocytes do not divide often
3 Types of Cartilage
• 1.) Hyaline
– Most common
– Looks like white glass
– Very find collagenous
fibers
– Found at the end of bones
and in the soft part of the
nose
– Important in the growth
and development of bones
• 2.) Elastic Cartilage
– Dense network
– More flexible than hyaline
– Provide framework of external ear parts and larynx.
• 3.) Fibrocartilage
– Very tough
– High in collagenous fibers
– Acts as a shock absorber
• Forms pads between the vertebra in the spinal column
• Cushions bones in your knees and pelvic girdle
Bone
• Most ridged connective tissue
• Hardens due to mineral salts: calcium carbonate
and calcium phosphate
• High in collagenous fibers
• Internally supports body structures
• Also protects the cranial and thoracic cavities
• Contains red blood cells (produced in the
marrow)
• Bone matrix is deposited in thin layers called
lamellae
• Bone cells are called osteocytes
– Located in the lacunae and evenly disrupted
• Osteons are a units made up of:
– Osteocytes
– Layers of extracellular matrix
Clustered together
around a central canal
• Also known as the Haversian system named for
Clopton Haversian.
• Each canal contains a blood vessel
• Material moves rapidly between blood vessels
and bone cells
Blood
• Transports a variety of materials between interior
body cells and those that exchange with the
environment.
• Blood is composed of 2 main parts:
– 1.) blood plasma – fluid extracellular matrix
– 2.) Formed Elements
• Red blood cells, white blood cells. And platelets
• Most blood is formed in the marrow of the long
bones.
5.4 Types of Membranes
• 5 types:
– 1. epithelial membranes- thin sheet like structures
composed to epithelium and underlying connective
tissue.
• 3 major types
– Serous
– Mucous
– cutaneous
– Serious membranes- line body cavities that lack
openings to the outside
• Consist of a layer of simple squamous epithelium and
thin layer of loose connective tissue
• Secrete serious fluid
– Mucous membrane- line cavities and tubes that open
to the outside of the body (ex.) oral and nasal
cavities)
• Consist of epithelium cells, goblet cells, and loose
connective tissue
• Cutaneous membranes – the skin
• Synovial membrane- lines the joints
5.5 Muscle Tissue
• General characteristics
– Able to contract
– Elongated cells often called muscle fibers
• Can contract (shorten and thicken)
– As they contract muscle fibers pull on the ends that are attached,
which causes movement.
– 3 types
• Skeletal (approx. 40% of the body)
• Smooth
• Cardiac
Skeletal Muscle Tissue
• Found in muscles that usually attach to bones
and controlled by conscious effort (voluntary
muscle tissue)
• Have striations – alternating light and dark cross
markings
• Each cells has multiple nuclei
Smooth Muscle Tissue
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Named because cell don’t have striations
Shorter than skeletal muscles and spindle shaped
Centrally located nucleus
Involuntary muscles
Cardiac Muscle Tissue
• Found only in the heart
• Cells are striated and branched, single nucleus
• Where cells touch each other is a special cell
junction called intercalated disc
• Involuntary muscle
5.6 Nervous Tissue
• Found in the brain, spinal cord, peripheral
nerves
• Basic cells are called neurons
• Respond to changes in the environment by
transmitting electrical impulses along axons
• As a result they can coordinate, regulate, and
integrate many body functions.
Nervous Tissue