Anatomy & Physiology
Chapter 4
Tissues
SUM 14
Matrix
1. Extracellular material
2. Much of matrix is secreted by cells
3. Composed of:
a. Fibrous proteins
b. Ground substance
1) Ground substance may also be
called:
•
•
Tissue fluid
Interstitial fluid
Extracellular fluid (ECF) Tissue gel
2) May be fluid, rubbery, or extremely
hard
Ground Substance
1. Unstructured material that fills empty
space between cells & fibers.
2. Typically functions to absorb compressive
forces and protect delicate cells, as well as
medium for diffusion
3. Consistency varies considerably and
depends on proportions of
a. Glycosaminoglycans (GAG’s)
b. Proteoglycans
c. Cell adhesion proteins (adhesive
glycoproteins)
Connective Tissue Fibers
1. Collagen
a. Tough and flexible, high tensile strength
b. 25% body’s protein
c. Tendons, ligaments, and dermis
2. Reticular
a. Fine fibers coated with glycoprotein
b. Delicate framework for spleen, lymph nodes
3. Elastic
a. Coiled elastin fibers stretch & recoil
b. Elasticity – ability to recoil
Cells
1. Blasts vs cytes
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

Chondroblasts
Fibroblasts
Osteoblasts
Glandular Epithelia
1. All galnds derived from epithelium
2. A gland is a cell or organ that secretes
substances for use elsewhere in the
body.
3. Secretion – the product and the process
of making and releasing product
4. Two types:
a. Exocrine glands – secrete into ducts
b. Endocrine glands - secrete product
directly into extracellular fluid
Glands
4. Some organs like pancreas & liver - dual
5. Unicellular gland
a. Exocrine cell in non-secretory
epithelium
Example: Goblet cell mucous cells
b. Mucin vs mucous
Unicellular Exocrine Gland
Microvilli
Secretory
vesicles
containing
mucin
Rough ER
Nucleus
Structure of a Gland
1. Many are enclosed in fibrous capsule
2. Extensions of capsule called septa or
trabeculae
a. Divides gland into lobes
3. Stroma – Connective tissue framework
4. Parenchyma – Functional tissue,
typically epithelium
Methods of Secretion
1. Merocrine glands
a. Exocytosis of secretory vesicles
b. Pancreas, most sweat glands, salivary
glands
2. Holocrine glands
a. Whole cell ruptures
b. Thick secretion contains synthesized
product and fragments of cell
c. Sebaceous glands of skin
3. Apocrine glands – In human, most are
probably merocrine
Merocrine
Gland
Types of Secretions
1. Serous glands
2. Mucous glands
a. Mucin + water yields mucus
3. Mixed glands
a. Combination of serous and
mucous cells
4. Cytogenic glands
Membranes
1. Cutaneous membrane
a. Largest in body, only external
membrane
b. Stratified squamous resting on
connective tissue (dermis)
c. Major difference from internal
membranes – DRY
d. Functions in protection
• Prevents dessication
• Forms barrier to pathogens and
mechanical injury
Internal Membranes
1. Mucous membranes
a. Line passageways that open to exterior
b. 2 or 3 layers:
i. Epithelium – type varies with location
ii. Lamina propria – areolar CT
iii. Sometimes muscularis mucosa
c. Function in absorption, secretion, and
protection
d. Mucus production - Goblet cells or
multicellular mucous glands or both
Mucous Membrane
Mucosa of
nasal cavity
Mucosa of
mouth
Esophagus
lining
Mucosa of
lung bronchi
(b) Mucous membranes line body cavities
open to the exterior.
Internal Membranes
2. Serous membranes
a. Simple squamous epithelium on thin
layer of areolar CT
i. Mesothelium vs. endothelium
b. Serous fluid – composition similar to
serum
c. Line internal body cavities and outer
surfaces of some organs
d. Lubrication and compartmentalization
Internal Membranes
3. Synovial membrane
a. Forms inner linings of freely moveable
joint cavities (synovial)
b. No epithelial component, only CT
c. Secrete thick synovial fluid into joint
cavity
d. Function in lubrication
Serous
Membranes
1. Pleura
2. Pericardium
3. Peritoneum
Parietal
pleura
Visceral
pleura
Parietal
pericardium
Visceral
pericardium
Change in Tissue Type
1. Differentiation – development of immature
tissue into a more specialized form
Ex. Embryonic mesenchyme to muscle
2. Metaplasia – some epithelia change
into another type of mature tissue
Ex. Smokers – pseudostratified columnar
epithelium to stratified squamous epithelium
Ex. Puberty – simple cuboidal epith. of
vagina changes to stratified squamous epith.
Tissue Growth
1. Hyperplasia – increase in number
of cells (mitosis)
2. Hypertrophy – increase in size of
existing cells
3. Neoplasia – abnormal, nonfunctional
tissue that forms tumor
Tissue Shrinkage & Death
1. Atrophy – shrinkage of tissue due to cell
death or reduced cell size
a. Senile atrophy
b. Disuse atrophy
2. Necrosis – premature pathological death
3. Gangrene – necrosis due to insufficient
blood flow
4. Infarction – sudden death of tissue
5. Apoptosis – programmed cell death of
excess or unnecessary cells
Tissue Repair
1. Regeneration
a. Replacement of dying cells with same
type of cells
b. Restores normal function
2. Fibrosis
a. Damaged tissue replaced with scar
tissue
b. Function not restored
Tissue Repair
1. Inflammation
1. Bleeding into wound carries antibodies, clotting
factors and white blood cells into injured area.
2. Scab formation seals wound and binds edges of
wound together. Macrophages are active cleaning up.
2. Organization - Fibroblasts and new capillaries
create granulation tissue.
3. Permanent Repair - Epithelium regenerates and
underlying connective tissue undergoes fibrosis.
1. Inflammation Sets
the Stage
a. Bleeding into
wound
b. Mast cells release
histamine
c. Plasma carries
antibodies,
clotting factors,
and WBC’s into
wound
1. Inflammation
a. Scab is body’s
band-aid –seals
wound and
binds edges
b. Macrophages
clean up debris
underneath
3. Organization restores
blood supply
a. New capillaries
grow into area to
form granulation
tissue
b. Fibroblasts build
new collagen
network
c. Begins day 3 or 4,
lasts up to 2 weeks
4. Permanent repair
a. Epithelium
regenerates under
scab and scab
sloughs off
b. Underlying CT
undergoes fibrosis
c. Scarring due to
fibrosis may fill in
by remodeling and
continued fibrosis
Regenerative Capacities
1. The capacity for regeneration varies widely
among different tissues
2. Tissues that regenerate well:
a. Epithelium
b. Bone
c. Areolar CT
d. Dense irregular CT
3. Moderate regenerative capacity:
a. Smooth muscle and dense regular CT
4. Poor regenerative capacity :
a. Cartilage and skeletal muscle
5. Cardiac muscle and CNS have virtually no
functional regenerative capacity
Developmental Aspects
1. Undifferentiated cells with potential to
become one or more types of mature
functional cells
a. Embryonic stem cells
i. Totipotent in early development
ii. Pluripotent after day 4 (blastocyst)
b. Adult stem cells – multipotent or
unipotent