TISSUES
HONORS ANATOMY &
PHYSIOLOGY
Tissues & Homeostasis
• 4 basic types of tissues in human
body contribute to homeostasis by
providing diverse functions including
• protection
• support
• communication among cells
• resistance to disease
• & many more
Definition
• a tissue is a group of similar cells that
usually have a common embryonic
origin & function together to carry out
specialized activities
Tissues
• their structure & properties are
influenced by factors such as:
– nature of the extracellular material
surrounding tissue cells
– type of connections between cells
Classification of Tissues
1. Epithelial
–
–
covers body surfaces & lines hollow organs,
cavities, & ducts
forms glands
2. Connective
–
protects & supports
3. Muscular
–
movement
4. Nervous
–
detects changes in/out body & responds by
generating action potentials
Embryology of Tissues
1. Epithelial
– from all 3 layers
2. Connective
– mesoderm
3. Muscular
– mesoderm
4. Nervous
– ectoderm
Cell Junctions
• are contact pts between plasma
membranes of adjacent cells
• found between most epithelial cells &
some muscle & nerve cells
Surfaces of Cells
Basement Membrane (bm)
• thin, extracellular layer
• commonly has 2 parts:
1. basal lamina
2. reticular lamina
Covering & Lining Epithelium
• classified according to 2 characteristics:
1. # of layers
• single layer = simple
• multiple layers = stratified
• single layer that looks like multiple =
psuedostratified
2. cell shape
• squamous
• cuboidal
• columnar
Simple Epithelium
1 layer of cells, often in sheets
functions:
diffusion/osmosis
filtration
secretion: production & release of
substances (sweat, mucus)
• absorption: intake of fluids or other
substances
•
•
•
•
•
Pseudostratified Epithelium
• appears to have multiple layers
because:
1. nuclei @ different layers
2. not all cells reach apical surface
Stratified Epithelium
• 2 or more layers of cells
– named by shape of top layer
• function: protection where there is
considerable wear & tear
Squamous Cells
• arranged like floor tiles
• very thin: allows for rapid passage of
substance thru cell
Cuboidal Cell
• shaped like cubes or hexagons
• +/- microvilli on apical surface
– finger-like cytoplasmic projections
– function increase surface area
• function: secretion or absorption
Columnar Cells
• taller than they are wide
• +/- microvilli or cilia on apical surface
– cilia: tiny hair-like projections that beat
in unison: moves substances across
surface of cell
•
•
•
•
function:
protection
absorption
secretion
Simple Squamous Epithelium
• single layer flat cells
• viewed from
– apical surface looks like tiled flooring
– cross-section: fried eggs cross section
Simple Squamous Epithelium
• found:
• @ sites where filtration (kidneys) or
diffusion (lungs, capillaries) occur
• lines blood vessels & chambers in
heart (endothelium), forms lining for
serous membranes (mesothelium)
Simple Cuboidal Epithelium
• nuclei round & centrally located
• functions:
– secretion
– absorption
• found in:
– thyroid gland
– kidneys
Simple Columnar Epithelium
• 2 forms: nonciliated/ciliated
• nonciliated simple Columnar
Epithelium
– 2 types:
1. Columnar epith. w/microvilli on apical
surfaces
2. Goblet cells
•
produce & secrete mucus
Ciliated Simple Columnar
Epithelium
• cilia on apical surface
• +/- Goblet cells
• functions:
– move mucus or any foreign objects away
from lower respiratory tract or ova
towards uterus
• found in:
– airways of upper respiratory system
– fallopian (uterine) tubes
Pseudostratified Columnar
Epithelium
• all cells attached to bm but not all
reach apical surface
• Ciliated Pseudostratified Columnar
Epith.:
• cells that do reach apical surface either
are goblet cells or are ciliated
• Nonciliated Pseudostratified Columnar
Epith:
• no cilia or goblet cells
Stratifed Squamous Epithelium
• basal layer continually undergoing cell
division
– as new cells grow, cells near base pushed
upward
– as near apical border moving farther
away from their blood supply (in
underlying connective tissue) 
dehydrate, shrink, harden, die  cell jcts
break down  cells sloughed off
Stratified Squamous Epithelium
• upper layers
contain keratin:
tough, fibrous
protein that
protects
underlying tissues
from heat,
microbes,
chemicals
• found: skin
• found: lining
mouth (buccal
mucosa) &
esophagus
• protect underlying
tissues from wear
& tear and from
invasion by
microbes
• Keratinized
• Nonkeratinized
Glandular Epithelium
• gland: single cell or group of cells that
secrete substances into:
– ducts
– onto a surface
– into blood
• classified:
1. endocrine
–
secretions  intercellular fluid  capillary
2. exocrine
–
secretions  ducts  surface of skin or
lining of hollow organ
Classification of Glands
Connective Tissue (CT)
• most abundant & widely distributed
tissue in body
• 2 basic elements:
1. extracellular matrix
2. cells
Extracellular Matrix
• greater % in CT than other tissues
• it’s the material located between cells
(secreted by those cells)
• determines qualities of the CT
• not usually found on surfaces, usually
rich blood supply (x cartilage & tendons)
• consists of:
– protein fibers
– ground substance
CT Cells
• immature form suffix “blast”
– large capacity to divide
– secrete matrix
• mature form suffix “cyte”
– less likely to divide
– maintain matrix
Fibroblasts
• large flat cells w/ branching processes
• found in most CT
• migrate thru CT secreting fibers &
ground substance
Macrophages
• develop from monocytes
• phagocytes
• irregular shape
• 2 types:
1. wandering
–
move to sites of infection or inflammation
2. fixed
–
–
reside in a particular tissue
ex: alveolar macrophages
Plasma Cells
• small cells that develop from B
lymphocytes
• Important in immune response
• most reside in CT
– GI & respiratory tracts
– lymph nodes, spleen, red bone marrow
Mast Cells
• found along side blood vessels that
supply CT
• produce & secrete histamine: dilates
small blood vessels as part of
inflammatory response (reaction to
injury or infection)
• can also bind, ingest, & kill bacteria
Adipocytes
• aka adipose cells or fat cells
• store triglycerides
• functions:
– store fats for nrg
– insulate
– cushion organs
Ground Substances
• acellular component of CT that supports
cells, binds them together, stores water,
provides medium thru which substances
are exchanged between blood & cells
• may be:
• fluid
• semifluid
• gelatinous
• calcified
CT Fibers: 3 Types
1. Collagen
–
–
“colla” = glue a protein (25% of all protein in body!)
very strong fibers that resist pulling
2. Elastic
–
–
–
smaller strong but stretchy fibers
made of protein called elastin
plentiful in skin, blood vessel walls, lung tissue
3. Reticular
–
–
made of collagen in fine tubes coated with
glycoproteins forming branching networks & found
in BM
skin, adipose, reticular CT (spleen, lymph nodes)
Mature CT: Loose CT
1. Areolar CT
• 1 of most abundant types
• includes all types of CT cells & fibers
• found in: subcutaneous tissue
Mature CT: Loose CT
2. Adipose Tissue
• cells: adipocytes
• found ass’c with areolar CT
• 2 types:
1. white
–
most of the adipose in adults
2. brown
–
–
darker due to rich blood supply
widespread in newborns: helps maintain
body temperature
Mature CT: Dense CT
• contains more numerous fibers but
fewer cells than in loose CT
• 3 types:
1. Dense Regular CT
2. Dense Irregular CT
3. Elastic CT
Dense Regular CT
• collagen fibers lined up in parallel
pattern allowing it to withstand
pulling aling axxis of fibers: very
strong tissue
• silvery white, tough
• ex: tendons & most ligaments
Dense Irregular CT
• collagen fibers irregularly arranged
• found where pulling forces exerted in
various directions
• found: dermis, pericardium,
periosteum
Elastic CT
• predominate fiber: elastic fibers
• quite strong & able to return to
original shape after being stretched
• found: elastic arteries, lungs
Membranes
• are flat sheets of pliable tissue that cover
or line a part of the body
• 2 types:
1. epithelial membrane:
–
–
epithelial layer + underlying CT
types: mucous membrane, serous
membrane, cutaneous membrane (skin)
2. synovial membrane:
–
–
+ CT but - epithelium
line joints
Mucous Membranes (Mucosa)
• line body cavities that open directly to
exterior
• line: entire digestive, upper respiratory,
& reproductive tracts
• cells connected by tight jcts
• Goblet cells secrete
1. mucus  slippery so prevents cavities from
drying out
2. enzymes from some
3. site of nutrient absorption
Serous Membranes (Serosa)
• line cavities that do not open directly to
exterior & covers organs w/in those cavities
• made of: areolar CT covered by mesothelium
(simple sq. epith.) which secretes serous fluid
• 2 layers:
1. parietal peritoneum
–
covers cavity wall
2. visceral peritoneum
–
–
–
covers organs
in pericardial cavity = pericardium
in abd. Cavity = peritoneum
CARTILAGE
• consists of a dense network of collagen
(strength) & elastic (flexibility) fibers, no
blood vessels or nerves (x
perichondrium) so heals very slowly
• chondrocytes: mature cartilage cells
– occur singly or in small groups w/in space
called lacunae
• perichondrium: membrane of dense CT
– covers surface of most cartilage
Cartilage
• 3 types:
1. Hyaline cartilage
–
–
most abundant cartilage in body, also the
weakest
provides flexibility & support
2. Fibrocartilage
–
–
no perichondrium
provides strength & rigidity (strongest of the
3)
3. Elastic cartilage
–
–
+ elastic fibers
provides strength & elasticity
Bone Tissue
• aka osseous tissue
• 2 types:
1. Compact bone
2. Spongy bone
Compact Bone
• basic unit of compact bone is the osteon
(haversian system)
• has 4 parts:
1. Lamellae
–
–
concentric rings of extracellular material &
collagen
make bone hard & strong
2. Lacunae
3. Canaliculi
4. Central (haversian) canal)
Spongy Bone
• lacks osteons
• found only inside compact bone
• consists of columns of bone called
trabeculae
– spaces between trabeculae filled with red
bone marrow
Blood
• liquid CT made up of:
• Plasma
– liquid portion of blood (yellow)
– water, dissolved nutrients, wastes, plasma
proteins, hormones, gases, ions
• RBCs: transport O2
• WBCs: phagocytes, immune response,
allergic reactions
• Platelets: cell particles involved in blood
clotting
Muscular Tissue
• consists of elongated cells called muscle
fibers that can use ATP to generate force
 movement, maintain posture,
generate heat
• 3 types:
1. Skeletal
2. Smooth
3. Cardiac
Skeletal Muscle Tissue
• most attached to a bone
• muscle fibers up to 12-16 in in
longest muscles:
– multinucleated (on edges)
– striated
– voluntary
Smooth Muscle Tissue
• in walls of hollow internal structures
– blood vessels
– urinary bladder
– intestines
• muscle fibers small, 1 centrally
located nuclei, +/- gap jcts
– nonstriated
– involuntary
Cardiac Muscle Tissue
• forms wall of heart
• muscle fibers are branched with 1
centrally located nuclei
– striated
– involuntary
– *intercalated discs: attach individual
fibers end-to-end (desmosome + gap jct)
allows for quicker conduction of action
potentials  coordinated contractions of
heart chambers
Nervous Tissue
• 2 cell types:
1. neurons
– nerve cells that can generate action
potentials which are conducted to other
neurons, muscles, or glands
2. neuroglia (glia)
– supportive cells to neurons
– cannot generate action potentials
Neurons
Action Potentials
• electrical excitability: ability to
respond to certain stimuli by
producing electrical signals (action
potentials)
• in neurons: travel (propagate) along
plasma membrane  release of
neurotransmitter
• in muscle fibers: action potentials
cause the fiber to contract (shorten)
Medical Terminology
• atrophy: decrease in size of cells 
decrease in size of organ
• hypertrophy: increase in size of a
tissue because its cells enlarge w/out
undergoing cell division