Notes – Unit 2: Histology
1. Histology is the study of tissues
a. A tissue is made up of a group of cells that are in the same
location and have the same function
2. Important Roots
a. Adip = fat
b. Chondr = cartilage
c. Cyt = cell
d. Epi = outer
e. Glia = glue
f. Inter = between
g. Macro = big
h. Oss= bone
i. Pseudo = false
j. Squam = scale
k. Strat = layer
3. There are 4 types of tissues
a. Epithelial – lines a body surface or cavity, can be glandular
b. Connective – connects things – bone, blood, fat…etc.
c. Muscle – muscles, organs that contract
d. Nervous – brain matter, nerves
4. Epithelial Tissue
a. Characteristics
i. Cellularity – composed almost entirely of cells
ii. Special contacts that form continuous sheets held together
by tight junctions and desmosomes
iii. Polarity – this means that there is a free upper surface and
an attached lower surface
iv. Covers organs, lines body cavities and hollow organs
1
v. Has a basement membrane – underside of the Epithelial
Tissue that is non-living and anchored to the Connective
Tissue
vi. Avascular – no blood supply
vii. Innervated – supplied by nerve fibers
viii. Regenerative – can rapidly replace lost cells
b. Functions of Epithelial Tissue
i. Protection
ii. Absorption
iii. Secretion
iv. Excretion
v. Filtration
vi. Sensory reception
c. How Epithelial Tissue is categorized
i. Number of Layers
1. Simple – one layer
2. Stratified – more than one layer
3. Pseudostratified – Single layer of cells, but the cells are
at different heights and give the appearance of multiple
layers
ii. Shape of the cells
1. Squamous - flat
2. Cuboidal – cube-shaped
3. Columnar – column-shaped
4. Transitional – change shape according to contents of
what it is lining
d. There are 9 specific types of Epithelial Tissue
i. Simple Squamous – functions in diffusion and filtration; discshaped nuclei; provide a slick, friction-reducing lining in the
lymphatic and cardiovascular systems; present in the kidney
2
ii.
iii.
iv.
v.
vi.
vii.
viii.
ix.
glomeruli, lining of the heart, blood vessels and lymphatic
vessels
Simple Cuboidal – functions in secretion and absorption;
nuclei shaped like spheres; found in the kidney tubules, ducts
and secretory portions of small glands and the ovary surface
Simple Columnar – oval-shaped nuclei, function in
absorption and secretion
1. Non-Ciliated – line the digestive tract and gall bladder
2. Ciliated – line small bronchi, uterine tubes, some
regions of the uterus
a. Cilia – help move substances through internal
passageways
Pseudostratified Columnar – function in secretion and
propulsion of mucous, present in the male sperm-carrying
ducts (non-ciliated) and trachea (ciliated)
Stratified Squamous – function in protection of underlying
areas subjected to abrasion, forms the external part of the
skin’s epidermis, linings of the esophagus, mouth and vagina
Stratified Cuboidal – rare, found in some sweat and
mammary glands
Stratified Columnar – limited distribution in the body, found
in the pharynx, male urethra and lining some glandular ducts,
might find in transition areas between two types of epithelia
Transitional – cells stretch to permit the distension of the
urinary bladder, found in the urinary bladder, ureters and
part of the urethra
Glands - a gland is one or more cells that makes and secretes
and aqueous fluid. Glands are classified by
1. Site of product release – endocrine or exocrine
2. Number of cells making the gland – unicellular or
multicellular
3
3. Types of Glands
a. Endocrine – ductless and make/ secrete hormones
– secrete within the body
b. Exocrine – more numerous than endocrine; secrete
products onto body surfaces or into body cavities;
types – mucous, sweat, oil, salivary
i. Unicellular Exocrine Gland – Goblet Cell –
makes Mucous
ii. Multicellular Exocrine Glands have a duct and
secreting unit
4. Glands can be classified by how they secrete their
products
a. Merocrine Glands secrete their products by
exocytosis (pancreas, sweat, salivary glands)
b. Holocrine Glands – secrete their products by the
rupturing of gland cells (sebaceous glands)
5. Connective Tissue – found throughout the body; most abundant
a. 4 Types of Connective Tissue
i. Connective Tissue Proper
ii. Cartilage
iii. Bone
iv. Blood
b. Functions of Connective Tissue
i. Binding and Support
ii. Protection
iii. Insulation
iv. Transporation
c. Characteristics of connective tissue
4
i. All originate from mesenchymal tissue during embryonic
development
ii. Vascularity
iii. Non-living extracellular MATRIX – made of Ground Substance
and Fibers
iv. Cells are further apart compared to Epithelial cells
d. 3 parts of Connective Tissue
i. Ground Substance – unstructured material that fills the space
between cells
ii. Fibers – collagen, elastic, reticular
iii. Cells – fibroblasts, chondroblasts, osteoblasts and
hemopoeitic stem cells
GROUND SUBSTANCE + FIBERS = MATRIX
e. Ground Substance – made of interstitial fluid and adhesion
proteins (fibronectin and lamnnin)
f. Fibers
i. Collagen – tough; provides tensile strength, make collagen,
most common
1. Found in Dense CT
ii. Elastic – long, thin fibers that allow for stretching, make
Elastin
iii. Reticular – branched collagenous fibers that form delicate
networks
1. Most thin, made of collagen
g. Cells Found In Connective Tissue
i. Fibroblasts – CT Proper
1. Most common, star-shaped, make fibers
ii. Chondroblasts – cartilage
iii. Osteoblasts – bone
iv. Hematopoietic Stem Cells – blood
5
v. White blood cells, plasma cells, macrophages and mast cells
– all involved in Immune Responses
vi. Mast Cells – large, usually near blood vessels
vii. Macrophages – defense
viii. Adipocyte – fat
h. The 4 types of Connective Tissue
i. Connective Tissue Proper – Loose and Dense
1. Loose CT – 3 types
a. Areolar CT
i. Gel-like matrix with all 3 connective tissue
fibers
ii. Fibroblasts, macrophages, mast cells, and
some white blood cells
iii. Wraps and cushions organs
iv. Widely distributed throughout the body
b. Adipose CT
i. Matrix is similar to Areolar CT with closely
packed adipoctyes
ii. Reserves food stores, insulates against heat
loss, supports and protects
iii. Found under skin, around kidneys, within the
abdomen and breasts
iv. Local fat deposits serve nutrient needs of
highly active organs
c. Reticular CT
i. Loose ground substance with reticular fibers
ii. Forms a soft internal skeleton, or stroma, that
supports other cells
iii. Found in lymph nodes, bone marrow and the
spleen
2. Dense CT – 2 types
6
a. Dense Regular
i. Parallel collagen fibers with a few elastic fibers
ii. Major cell type is fibroblasts
iii. Attaches muscles to bone or to other muscles
and bone to bone
iv. Found in tendons and ligaments
b. Dense Irregular
i. Irregularly arranged collagen fibers with some
elastic fibers
ii. Main cell type is fibroblasts
iii. Withstands tension in many directions
providing structural strength
iv. Found in the dermis, submucosa of the
digestive tract, and fibrous organ capsules
3. Cartilage – 3 types
a. Hyaline Cartilage
i. Amorphous, firm matrix with imperceptible
network of collagen fibers
ii. Supports, reinforces, cushions and resists
compression
iii. Forms the costal cartilage – on your ribs
iv. Found in the embryonic skeleton, ends of long
bones, nose, trachea and larynx
b. Elastic Cartilage
i. Similar to hyaline cartilage but with more
elastic fibers
ii. Maintains shape and structure while allowing
flexibility
iii. Supports the external ear (pinna) and the
epiglottis (covering of the windpipe
c. Fibrocartilage
7
i. Matrix similar to hyaline cartilage but less firm
with thick collagen fibers
ii. Provides tensile strength and absorbs
compression shock
iii. Found in intervertebral discs, pubic symphysis
and in discs of the knee joint
4. Bone (Osseus) Tissue
a. Hard, calcified matrix with collagen fibers found in
bone
b. Osteocytes are well vascularized
c. Supports, protects and provides levers for muscular
action
d. Stores calcium, minerals and fat
e. Marrow inside of bones is the site of hemopoiesis
5. Blood – only liquid connective tissue
a. Two parts – Formed Elements and Plasma
b. Contained within blood vessels
c. Functions in the transport of respiratory gases,
nutrients and wastes
6. Nervous Tissue
a. Branched Neurons with long cellular processes and support cells
called Neuroglia
b. Transmits electrical signals from sensory receptors to effectors
c. Found in the brain, spinal cord, and peripheral nerves
7. Muscular Tissue
a. 3 types of Muscular Tissue
i. Skeletal
1. Long, cylindrical, multinucleated cells with obvious
striations
2. Initiates and controls voluntary movement
3. Found in skeletal muscles that attach to bones or skin
8
ii. Cardiac
1. Branching, striated, uninucleated cells interlocking at
intercalated discs
2. Propels blood into the circulation
3. Found in the walls of the heart
4. Involuntary
iii. Smooth
1. Sheets of spindl-shaped cells with central nuclei and no
striations
2. Propels substances along internal passageways
3. Found in the walls of hollow organs
4. Involuntary
8. Epithelial Membranes
a. Cutaneous – skin
b. Mucous – lines body cavities open to the exterior
c. Serous – moist membranes found in closed ventral body cavity
9