2 or more cell layers
Basement membrane consists of ___ ____ & ____ _____.
basal lamina and reticular lamina
deep to the basal lamina, part of the connective tissue
Five distinguishing characteristics of epithelial tissue?
- 1. polarity
- 2. specialized contacts
- 3. supported by connective tissues
- 4. avascular but innervated
- 5. ability to regenerate
3 main areas formed by epithelial tissue?
- 1. covers body surfaces
- 2. lines cavities
- 3. forms glands
How do cancer cells react to basement membrane differently than regular cells?
Cancerous cells do not respect the boundary of basement membrane so they penetrate the tissues beneath it
All epithelial tissues have an ____ surface that is the upper surface exposed to body exterior or the cavity of an internal organ and a lower attached _____ surface.
tiny hair-like projections that move and propel substances along their surface
line the trachea
6 functions of epithelial tissue?
- 1. protection
- 2. absorption
- 3. filtration
- 4. excretion
- 5. secretion
- 6. sensory reception
Based on number of cell layers there are ___ and ____ epithelia.
simple and stratified
What causes epithelial polarity?
Apical-basal polarity: apical and basal surfaces differ in structure and function
How are epithelial tissues named?
each epithelium has 2 names: first indicates number of cell layers and second describes shape of its cells
What is epithelial tissue?
sheet of cells that covers the body or lines body cavities
groups of cells similar in structure and function
4 types of basic tissues in the body?
- 1. epithelial tissue
- 2. muscular
- 3. connective
- 4. nervous tissue
Why must nearly all substances received or given off by the body pass through epithelial tissue?
epithelium forms boundaries between environments
Example: boundary between bladder and urine in the bladder
The study of tissue?
single layer of cells
How are epithelial tissues nourished since they contain no blood vessels?
blood vessels in underlying connective tissues
Where are simple epithelia normally found?
where absorption, secretion, and filtration occur
finger-like extensions of apical surface that increase surface area for absorption and secretion
Where is stratified epithelia usually found?
high-abrasion areas where protection is important: skin, lining of the mouth
adhesive sheet that filters what diffuses from underlying connective tissue into epithelium and acts as a scaffolding where epithelial cells can migrate to repair a wound
- flattened and scale-like
boxlike, approximately as tall as they are wide
- tall and column shaped
Shape of nucleus in squamous, cuboidal, and columnar cells?
- Nucleus takes shape of cell:
- squamous is disc shaped
- cuboidal is spherical
- columnar is oval shaped and usually close to bottom of the cell
In stratified epithelia where there may be several cell shapes, how are they named?
based on apical layer cell shape
flattened and scale-like
Where is simple squamous epithelium usually found and why?
found where filtration or the exchange of substances by rapid diffusion is a priority because they are thin and often permeable
Functions of simple squamous tissue?
allows materials to pass by diffusion and filtration in sites where protection is not important
secretes lubricating substances in serosae
Where is simple squamous epithelium found?
- 1. kidney glomeruli
- 2. air sacs of lungs
- 3. lining of heart, blood vessels, and lymphatic system
- 4. lining ov ventral body cavity (serosae)
2 types of simple squamous epithelia in the body that have special names that reflect their location?
- 1. endothelium
- 2. mesothelium
Where is endothelium found?
- 1. lining of lymphatic vessels
- 2. in all hollow organs of the cardiovascular system: BV's and the heart
- 3. capillaries (exclusively made of endothelium)
Why are capillaries made exclusively of endothelium?
its thinness encourages the efficient exchange of nutrients and wastes between the bloodstream and surrounding tissues
3 areas where mesothelium is found?
- 1. serous membranes
- 2. membranes lining the ventral body cavity
- 3. covering organs of the ventral body cavity
2 important functions of simple cuboidal tissue?
secretion and absorption
Where is simple cuboidal tissue found?
kidney tubules, ducts and secretory portions of small glands, and ovary surface
Function of cilia on apical surface of columnar epithelium?
propel mucus or reproductive cells
Where are non-ciliated and ciliated simple columnar epithelium found?
non-ciliated: lines most of digestive tract, gallbladder, and excretory ucts of some glands
ciliated: lines small bronchi, uterine tubes, and some regions of the uterus
Functions of simple columnar epithelium
absorption and secretion:
secretion of mucus, enzymes, and others
What 2 modifications does the digestive tract have to its simple columnar epithelium to increase absorption and secretion?
- 1. dense microvilli on apical surface
- 2. tubular glands made primarily of cells that secrete mucus-containing intestinal juice
____ _____ epithelium lines the digestive tract from the stomach through the rectum.
Pseudostratified columnar epithelium?
Columnar epithelium where all cells touch basement membrane but are of varying heights
Where is pseudostratified epithelium found?
nonciliated type in sperm-carrying ducts and ducts of large glands
ciliated type lines the trachea and most of the upper respiratory tract
Function of pseudostratified columnar epithelium?
same as columnar epithelium: secretion and absorption
mainly secrete mucus and propel it with cilia
What type of epithelium lines most of the respiratory tract?
pseudostratified columnar epithelium with cilia and mucus-secreting goblet cells
goblet cells make mucus that traps particles and dust and cilia sweeps it away from the lungs
contains 2 or more cell layers
Main function of stratified epithelia?
How does stratified epithelia regenerate?
regenerates from below: basal cells divide and push apically to replace the older surface cells
Composition of stratified squamous epithelium?
free surface cells are squamous and cells of deeper layers are cuboidal or columnar -
Where is stratified squamous epithelium found?
forms the external part of the skin and extends a short distance into every body opening directly continuous with the skin
Why are cells farther from the basement membrane in stratified squamous tissue less viable then those near the basement membrane?
because epithelium depends on nutrients from the deeper connective tissue
Where is nonkeratinized stratified squamous epithelium found?
forms the moist linings of the esophagus, mouth, and vagina
How does the epidermis (outer layer of skin) differ from other stratified squamous epithelia of the body?
it is keratinized - contains the protein keratin that makes it tougher
Where is stratified cuboidal tissue found?
- rare- found in larger glands: sweat glands, mammary glands
Where is stratified columnar epithelium found?
rare: small amnts in pharynx, male urethra, lining some glandular ducts, and at transition areas or junctions between 2 other types of epithelia
Composition of stratified columnar epithelium?
only apical layer is columnar
Where is transitional epithelium found?
lining of hollow urinary organs which stratch as they fill with urine
Composition of transitional epithelium?
- cells of basal layer are cuboidal or columnar
- apical cells vary in appearance depending on the degree they are stretched
one or more cells that make and secrete a particular product
product secreted by a gland: usually a water-based fluid containing protein
2 ways glands are classified?
- 1. where they release their product
- 2. number of cells: unicellular, multicellular
produce hormones that are secreted by exocytosis directly into the extracellular space where they enter blood or lymph
secrete their products onto body surfaces or into body cavities
Unicellular exocrine glands secrete products by ____ and multicellular do so via a ____ that transports secretions to epithelial surface.
Products secreted by exocrine glands?
mucous, sweat, oil, saliva, bile in the liver, pancreatic enzymes, and many others
2 only important examples of unicellular exocrine glands?
mucous cells and goblet cells
glycoprotein produced by unicellular exocrine glands that dissolves in water when secreted and forms mucus
unicellular exocrine glands that produce mucus and are shaped like a wine glass
Composition of multi-cellular exocrine glands?
2 basic parts: a duct and a secretory unit (acinus) with supportive connective tissue that surrounds the secretory unit and divides into lobes usually
How are multicellular exocrine glands classified>
structure and type of secretion
On the basis of their duct structures multicellular exocrine glands are either ____ or ____
- simple - unbranched duct
- compound - branched duct
3 multicellular exocrine gland classifications based on their secretory units?
- 1. tubular - secretory cells form tubes
- 2. alveolar - form sacs
- 3. tubuloalveolar - have tubes and sacs
3 classifications of multicellular exocrine glands based on how they secrete their products?
merocrine glands, holocrine glands, and apocrine glands
How do merocrine glands secrete their product?
secrete by exocytosis without altering the cell
think "merely secrete"
Where are merocrine glands found?
pancreas, most sweat glands, and salivary glands
How do holocrine glands secrete their product?
accumulate their products within them until the rupture then are replaced by division of underlying cells
Only example of holocrine glands?
sebaceous (oil) glands of the skin
___ tissue is the most abundant and widely distributed tissue in the body.
4 main classes of connective tissue?
- 1. connective tissue proper
- 2. cartilage
- 3. bone
- 4. blood
5 main functions of connective tissue?
- 1. binding and supporting
- 2. protecting
- 3. insulating
- 4. storing reserve fuel
- 5. transporting substances within the body
3 common characteristics of connective tissue?
- 1. common origin: all arise from the mesenchyme (an embryonic tissue)
- 2. degrees of vascularity: some are avascular & some are very vascular
- 3. extracellular matrix: connective tissues are largely nonliving extracellular matrix
What makes connective tissue able to withstand great tension and abuses that other tissues cannot?
they are mostly composed of extracellular matrix
3 main elements of connective tissue?
- 1. ground substance
- 2. fibers
- 3. cells
ground substance and fibers make up the extracellular matrix
unstructured material that fills the space between cells and contains the fibers
Ground substance is composed of what 3 things?
- 1. interstitial fluid
- 2. cell adhesion proteins
- 3. proteoglycans
Function of cell adhesion proteins?
glue that allows connective tissue cells to attach to matrix elements
Why does the ground substance contain a large amnt of fluid?
functions as a medium through which nutrients and other dissolved substances can diffuse between blood capillaries and the cells
3 types of fibers found in connective tissue?
collagen, elastic, and reticular fibers
What are fibers made of?
made of collagen - provided high tensile strength (ability to resist being pulled apart) to the matrix
Why do collagen fibers provided ability to resist being pulled apart?
their fibrils are cross-linked so they hold together
What type of protein makes up elastic fibers?
What does this allow elastic fibers to do?
allows them to stretch and recoil like a rubber band
How far can connective tissues stretch?
can stretch until collagen fibers become taut then elastic fibers snap them back to normal length and shape
Where are elastic fibers found in connective tissue?
found where greater elasticity is needed: skin, lungs, and blood vessel walls
collagenous fibers that are continuous with collagen fibers but are smaller - branch out and form webs with more give than collagen fibers
Where are reticular fibers found?
surround small blood vessels, support soft tissue of organs
particularly found where connective tissue meets other tissue
What type of cells does connective tissue have?
each major class of connective tissue has a resident cell type
What are immature cells called?
What are mature cells called?
Function of immature cells (-blasts)?
actively mitotic cells that secrete the ground substance and the fibers characteristic of their particular matrix
Primary blast cell types by connective tissue class?
- 1. connective tissue proper: fibroblast
- 2. cartilage: chondroblast
- 3. bone: osteoblast
- 4. blood: hematopoietic stem cell is the blast cell that produces blood cells but it is not located in blood and does not produce the fluid matrix of blood
What happens to blast cells once they synthesize the matrix?
mature and less active (get old and sit around) and have the suffix (-cyte)
mature cells maintain health of the matrix
What may happen to mature cells if the matrix of connective tissue is injured?
they can revert to their blast state to repair and regenerate the matrix
4 cell types contained in connective tissue other than the major types according to type of connective tissue?
- 1. fat cells
- 2. white blood cells
- 3. mast cells
- 4. macrophages
Function of fat cells?
Where are mast cells usually located?
typically cluster along blood vessels
Function of mast cells?
detect foreign microorganisms and initiate local inflammatory responses against them
What do mast cells contain in their cytoplasm?
secretory granules with chemicals that mediate inflammation especially in severe allergies: heparin, histamine, proteases, and other enzymes
substance that makes capillaries leaky
large, irregularly shaped cells that devour a broad variety of foreign materials: bacteria, dust, dead tissue cells
important to immune system
What connective tissues are considered to be connective tissue proper?
all connective tissues except cartilage, bone, and blood
2 subclasses of connective tissue proper?
- 1. loose connective tissue
- 2. dense connective tissue
3 types of loose connective tissues?
- 1. areolar
- 2. adipose
- 3. reticular
3 types of dense connective tissues?
- 1. dense regular
- 2. dense irregular
- 3. elastic
Composition of areolar connective tissue?
gel-like matrix with all 3 fiber types that are loosely arranged
5 types of cells in areolar connective tissue?
fibroblasts, macrophages, mast cells, fat cells, and some WBC's
Most abundant cell type in areolar connective tissue?
Why are areolar tissue fibers loosely arranged?
allows for reservoir of water and salts for surrounding body tissues, always holds approx. as much fluid as there is in the entire bloodstream
Essentially all body cells obtain their nutrients from and release their wastes into what type of connective tissue fluid?
4 major functions of areolar connective tissue?
- 1. wraps and cushions organs
- 2. macrophages phagocytize bacteria
- 3. important role in inflammation
- 4. holds and conveys tissue fluid
What may hinder the movement of cells through the ground substance of areolar tissue?
How do WBC's get around this?
high content of hyaluronic acid makes ground substance viscous like molasses
WBC's secrete hyaluronidase, an enzyme that liquefies ground substance - some harmful bacteria can also do this
___ connective tissue is the most widely distributed connective tissue in the body and serves as a universal packing material between other tissues.
Areolar connective tissue is present in mucous membranes as the ___ ____.
Composition of adipose tissue?(fat tissue)
- similar to areolar tissue in structure and function but has higher nutrient-storing ability and is 90% adipose cells- looks like chicken wire
Why is adipose tissue richly vascularized?
it has high amount of metabolic activity
Where does adipose tissue accumulate?
Where is it mostly found?
mostly found in subcutaneous tissue
also found around the kidneys behind eyeballs, genetically determined fat deposits, around high energy organs like heart and lymph nodes
Functions of adipose tissue?
- 1. shock absorption
- 2. insulation
- 3. energy storage
Why are there fat deposits around high-energy organs like the heart?
provide nutrient needs to active organs
does not do other functions of adipose tissue - uses stored energy to create heat in the bloodstream - mostly found in babies because they lack ability to produce body heat by shivering
Reticular connective tissue composition?
resemble areolar connective tissue but only has reticular fibers in matrix with reticular cells
Function of reticular connective tissue?
fibers form a soft internal skeleton (stroma) that supports other cell types: WBC's, mast cells, and macrophages
Where is reticular connective tissue located?
lymphoid organs: lymph nodes, bone marrow, and spleen
Why are dense connective tissues also called fibrous connective tissues?
fibers are their prominent element
Composition of dense regular connective tissue?
- closely packed bundles of collagen fibers running in same direction parallel to the direction of pull: flexible with great resistance to tension
Cells of dense regular connective tissue?
very few cells other than fibroblasts that continuously make collagen fibers
Vascularization of dense regular connective tissue?
Where is dense regular connective tissue found?
- 1. tendons: attach muscle to bone
- 2. aponeuroses: flat sheet-like tendons that attach muscles to other muscles or to bones
- 3. ligaments: bind bones to joints
- 4. fascia: wraps around muscles, blood vessels, and nerves
Dense irregular connective tissue composition?
- similar to dense regular but collagen fibers are arranged irregularly
Functions of dense irregular connective tissue?
withstands tension exerted in many directions and provides structural strength
Where is dense irregular tissue found?
- 1. fibrous capsules of organs and joints: kidneys, bones, cartilages, muscles, and nerves)
- 2. dermis of the skin
- 3. submucosa of the digestive tract
Elastic connective tissue?
- dense regular connective tissue containing a high proportion of elastic fibers
3 functions of elastic connective tissue?
- 1. allows tissue to recoil after stretching
- 2. maintains pulsatile flow of blood through arteries
- 3. aids passive recoil of lungs following inspiration
Where is elastic connective tissue located?
walls of large arteries, within certain ligaments associated with the vertebral column, within the walls of the bronchial tubes
has qualities between those of dense connective tissue and bone: stands up to tension and compression
Nerves and vascularization of cartilage?
lacks nerve fibers and blood vessels
How is cartilage nourished?
receives nutrients by diffusion from blood vessels located in connective tissue layer surrounding it
Composition of cartilage?
ground substance contains large amounts of chondroitin sulfate and hyaluronic acid, collagen fibers, and are 80% water
What allows cartilage to rebound after being compressed and helps to nourish cartilage cells?
high content of water in ground substance of cartilage
What is the predominant cell type in growing cartilage and what is its function?
chondroblasts - produce new matrix until the skeleton stops growing at the end of adolescence
cavities in the cartilage that contain small groups of chondrocytes
Why does injured cartilage heal slowly?
cartilage is avascular and aging cartilage cells lose their ability to divide
3 types of cartilage?
Each is dominated by a particular fiber type
- 1. hyaline cartilage
- 2. elastic cartilage
- 3. fibrocartilage
Most abundant cartilage in the body?
Composition of hyaline cartilage?
contains large number of collagen fibers but appears glassy
Where is hyaline cartilage found?
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
Functions of hyaline cartilage?
- 1. supports and reinforces
- 2. serves as resilient cushion
- 3. resists compressive stress
hyaline cartilage the covers the ends of long bones and provides a pad to absorb compression at joints
Composition of elastic cartilage?
similar to hyaline cartilage but more elastic fibers in matrix
Function of elastic cartilage?
maintains shape while allowing great flexibility
Where is elastic cartilage found?
external ear (pinna), epiglottis
Composition of fibrocartilage?
- intermediate between hyaline cartilage (rows of chondrocytes) and dense regular connective tissues (rows of collagen fibers)
Function of fibrocartilage?
tensile strength allow it to absorb compressive shock
Where is fibrocartilage found?
intervertebral discs, pubic symphysis, discs of the knee joint
Composition of bone?
- similar to cartilage but has more collagen fibers and added matrix element: calcium salts...has structural units called osteons formed of rings of bony matrix (lamellae) surrounding central canals that contain blood vessels and nerves serving the bone
Function of osteoblasts?
produce the organic portion of the matrix
Where are osteocytes in bone?
in lacunae within the matrix produced by osteoblasts
Functions of bone?
- 1. supports and protects (by enclosing)
- 2. provides levers for the muscles to act on
- 3. stores calcium and other minerals and fat
- 4. marrow inside bones is site for blood cell formation (hematopoiesis)
Composition of blood?
consists of blood cells surrounded by a nonliving fluid matrix called blood plasma
3 types of blood cells?
RBC's are most abundant, WBC's, and platelets
Fibers of blood?
protein molecules that form visible fiberlike structures during blood clotting
Function of blood?
transport respiratory gases, nutrients, wastes, and other substances
___ tissues are highly cellular, well vascularized tissues that are responsible for most types of body movement.
elaborate networks of actin and myosin filaments that bring about movement of contraction in all cell types
3 types of muscle tissue?
- 1. skeletal
- 2. cardiac
- 3. smooth
skeletal muscle -within voluntary control
cardiac and smooth
Composition of skeletal muscle?
composed of long, cylindrical, multinucleate cells with obvious striations
Functions of skeletal muscle?
voluntary movement, locomotion, manipulation of the environment, facial expression, voluntary control
Where is skeletal muscle found?
attached to bones or occasionally to skin
Composition of cardiac muscle?
- cells are striated like skeletal muscle, cells have only one nucleus, contain intercalated discs: unique junctions where branching cells fit together tightly
Composition of smooth muscle?
spindle-shaped (elongated) cells with one nucleus; no striations, cells arranged closely to form sheets
Components of the nervous system that is made up of nervous tissue?
brain, spinal cord, and nerves
Function of the nervous system?
regulates and controls body functions
2 major cells types of nervous tissue?
neurons and supporting cells
highly specialized nerve cells that generate and conduct nerve impulses
Composition of a neural tissue?
branching cells with cell process that may be long and extend from the nucleus-containing cell body (called axon)
Functions of supporting cells?
support and protect neurons
Supporting cells are also know as ___ cells or ___.
glial cells or neuroglia
Three types of membranes?
cutaneous, mucous, or serous
Composition of membranes
all are continuous multicellular sheets composed of at least 2 primary tissue types: an epithelium bound to an underlying layer of connective tissue proper
Cutaneous membrane composition?
skin - keratinized stratified squamous epithelium (epidermis) firmly attached to a thick layer of connective tissue (dermis)
How is cutaneous membrane different from other membranes?
exposed to the outside and is dry
Mucous membranes? (mucosae)
line all body cavities that open to the outside of the body; wet/moist with secretions/urine in urinary system
Composition of mucous membranes?
most are stratified squamous or simple columnar epithelia directly over a layer of loos e connective tissue called the lamina propria
loose connective tissue that is connected to mucous membranes
Main areas where mucous membranes are found?
What is their function?
hollow organs of the digestive tract, respiratory tract, and urogenital tract
absorption and secretion: secrete mucus in digestive and respiratory tracts
moist membranes found in closed ventral body cavities
Composition of serous membranes?
simple squamous epithelium (a mesothelium) resting on a thin layer of loose connective (areolar) tissue
How is serous fluid in serous membranes created?
mesothelial cells add hyaluronic acid to the fluid that filters from the capillaries in the associated connective tissue: results in serous fluid that lubricates surfaces of parietal and visceral layers
line the thoracic wall and cover the lungs
encloses the heart
encloses the abdominopelvic viscera
relatively nonspecific reaction that develops quickly wherever tissue damage occurs
extremely specific response that takes longer than inflammatory response
Tissue repair requires that cells ____ and migrate, activities that are initiated by ___ ____ released by injured cells.
divide and migrate
2 major ways tissues are repaired?
- 1. regeneration
- 2. fibrosis
replaces destroyed tissue with the same kind of tissue
dense connective tissue proliferates to form scar tissue
How is it decided whether tissue damage will be repaired by regeneration or fibrosis?
depends on the type of tissue damaged and the severity of the damage
Steps of tissue repair?
- 1. Injured tissue cells release inflammatory
- chemicals --> cause capillaries to dilate -->
- capillaries are more permeable
- 2. WBC's & plasma (clotting factors,
- antibodies, etc) seep into area
- 3. Clotting factors construct a clot: stops
- bleeding and walls in injured area
- 4. Blood clot is replaced by granulation
- 5. Surface epithelium regenerates under the
- scab and the scab detaches
- 6. end result is fully regenerated epithelium
- with underlying scar tissue that may be
- visible or invisible
What happens to the excess fluid, destroyed cells, and other debris that occurs r/t tissue damage and inflammatory response?
removed via lymphatic vessels or by macrophages
first phase of tissue repair where clot is replaced by granulation tissue
delicate pink tissue that contains capillaries that grow in from nearby areas and lay down new capillary bed
Cells found in granulation tissue?
What is their function?
fibroblasts: produce growth factors and new collagen fibers
some have contractile properties that allow them to pull the margins of the ound together or pull existing blood vessels into the healing wound
What happens to the original blood clot during organization stage of tissue repair?
macrophages digest it and collagen fiber deposits replace it
What will granulation tissue become?
Why is granulation tissue highly resistant to infection?
produces bacteria-inhibiting substances
What happens to fibroblasts once matrix has been formed during tissue repair?
revert to resting state or undergo apoptosis (cellular suicide)
What form of tissue repair occurs in simple infections such as a sore throat?
Tissues that regenerate extremely well?
epithelial tissue, bone, areolar connective tissue, dense irregular connective tissue, and blood-forming tissue
Tissues that have a moderate capacity for regeneration?
smooth muscle and dense regular connective tissue
Tissues with a weak regenerative capacity?
skeletal muscle and cartilage
Tissues with virtually no functional regenerative capacity?
cardiac muscle and nervous issue in the brain and spinal cord
pale, often shiny area composed mostly of collagen fibers: strong but less flexible than most normal tissues and cannot perform functions of tissue it replaced
How can scar tissue effect internal organs?
Scar tissue shortens area and can cause hollow organs to become smaller on the inside, can also cause adhesions that bind 2 organs together that can prevent intestines from moving freely and obstruct flow of food
3 layers of the primary germ layer? (one of the first things developed during embryonic development)
ectoderm, mesoderm, and endoderm
What do the primary germ layers become?
specialize to become the 4 primary tissue types
When during embryonic development have all the primary tissues appeared all major organs are in place?
What happens to embryonic cells during fetal period and up to birth?
most cells remain mitotic and produce rapid growth; division of nerve cells stops or nearly stops during the fetal period; all other cells continue to grow until adulthood
In adults only ____ and ____ cells are highly mitotic
epithelia and blood
What occurs in tissues as we age?
Epithelia thin and are easily penetrated; tissue repair is less efficient; bone, muscle, and nervous tissues atrophy (especially if not physically active)
decreased circulation is a factor in some of these changes