Tissue

Chapter 4
Tissues, Glands,
& Membranes
1
General Definitions:
•
Tissue - group of cells similar structure
and function along with similar
extracellular substances between the
cells
• Histology – microscopic study of tissue
structure
• Histo- = tissue, -ology = study
2
Causes of Tissue Change
Development
 Growth
 Aging
 Trauma
 Disease

3
Four Basic Types of Tissues

Epithelial tissues

Epi = on + thele = covering or lining
Connective tissues
 Muscle tissues
 Nervous tissues

4
Epithelial Tissue, General Characteristics
• Covers internal and external body
surfaces
• Skin, digestive tract, respiratory
passages, and blood vessels
• Comprises major tissue of glands
5
Epithelial Tissue, Unique characteristics


Consists mostly of cells
with very little
extracellular material
(matrix or ECM)
Lacks blood vessels

Gases, nutrients, &
waste diffuse across
basement membrane


Cells attached to
underlying tissue
Free membrane is not
touching any other cells
6
Functions of Epithelial Tissue
• Protect underlying structures
•
Skin & oral cavity
• Barrier
•
Skin keeps water in/out, prevents entrance of toxins
& microorganisms
• Exchange of substances
•
O2 & CO2 diffused through lung epithelia between air
and blood
• Secretion
•
Sweat glands, mucous glands, pancreas
• Absorption
•
Carrier molecules in intestine absorb nutrients
(vitamins, ions, food molecules)
7
Classification of Epithelia
• Classified based on number of cell layers
and cell shape
• Simple epithelium – 1 layer of cells
• Stratified epithelium - >1 layer of cells
• Squamous (flat and scale-like)
• Cuboidal (cube shaped)
• Columnar (tall and thin)
8
Layers or “Arrangement”
9
Shapes
10
11
Types of Epithelia
1) Simple squamous epithelia (lungs)
2) Simple cuboidal epithelia
3) Simple columnar epithelia
4) Pseudostratified columnar epithelia (w/cilia)
(trachea)
5) Stratified squamous epithelia
6) Transitional epithelium (bladder)
12
Simple Squamous Epithelium
• Single layer of thin, flat
cells
• Line blood vessels,
lymphatic vessels,
heart, alveoli, kidney
tubules, serous
membranes
• Diffusion, filtration,
anti-friction, secretion,
absorption
13
Simple Cuboidal Epithelium

Single layer of cubeshaped cells, some
with microvilli or cilia
 Kidney tubules,
glands/ducts, brain,
bronchioles, ovary
surface
 Secretion,
absorption,
movement of
particles
14
Simple Columnar Epithelium

Single layer of tall,
narrow cells, some with
cilia/microvilli
 Lining of stomach,
intestines, glands,
ducts, bronchioles,
auditory tubes, uterus,
uterine tubes
 Secretion, absorption,
movement of
particles/oocytes
15
Pseudostratified Columnar
Epithelium

Single layer of cells,
some tall and thin,
others not, nuclei at
different levels,
appear stratified,
almost always
ciliated
 Lining of nasal
cavity, nasal
sinuses, auditory
tubes, pharynx,
trachea, bronchi
 Synthesis/secretion/
movement of mucus
16
Transitional Epithelium

Stratified cells
appear cuboidal
when not stretched
and squamous when
stretched
 Lining of bladder,
ureters, superior
urethra
 Deals with changing
volume of fluid in an
organ, protects from
urine contact
17
Simple Columnar Epithelium
18
Simple Squamous Epithelium
19
Stratified Squamous Epithelium
20
Simple Cuboidal Epithelium
21
Stratified Columnar Epithelium
22
Pseudostratified Columnar Epithelium
23
Transitional Epithelium
[bladder]
24
Stratified Cuboidal Epithelium
25
26
27
28
29
30
31
Structural & Functional
Relationships

Cell Layers & Cell Shapes

Single layers – control passage of materials
through epithelium
Gas diffusion across lung alveoli
 Fluid filtration across kidney membranes
 Gland secretion
 Nutrient absorption in intestines


Multiple layers – protect underlying tissues
Damaged cells replaced by underlying cells
 Protect from abrasion (ex: skin, anal canal,
vagina)

32
Structural & Functional
Relationships

Cell Layers & Cell Shapes, continued

Flat/thin (squamous) – diffusion, filtration
Diffusion in lung alveoli
 Fluid filtration in kidney tubules


Cuboidal/columnar – secretion, absorption;
contain more organelles

Secretory vesicles (mucus) in stomach lining


Mucus protects against digestive enzymes and acid
Secretion/absorption in kidney tubules made
possible by ATP production by multiple
mitochondria

Active transport of molecules into/out of kidney
33
Structural & Functional
Relationships

Free Cell Surfaces

Smooth – reduces friction


Microvilli – increase cell surface area; cells
involved in absorption or secretion


blood vessel lining – smooth blood flow
Small intestine lining
Cilia – propel materials along cell’s surface
Nasal cavity/trachea – moves dust and other
materials to back of throat (swallowed/cough up)
 Goblet cells secrete mucus to entrap the “junk”

34
Structural & Functional
Relationships

Cell Connections



Tight junctions – bind adjacent cells together
 Permeability layers – prevent passage of materials
 Intestinal lining and most simple epithelia
Desmosomes – anchor cells to one another
 Hemidesmosomes – anchor cells to basement
membrane
 Epithelia subject to stress (skin stratified squamous)
Gap Junctions – allow passage of molecules/ions
between adjacent calls (communication)
 Most epithelia
35
Cell Connections
36
Glands

Gland – multicellular structure secreting
substance onto a surface, into a cavity, or into
the blood

Exocrine gland (exo-outside + krino-to separate): glands
with ducts; secretions pass through ducts onto a
surface or into an organ





Simple – ducts w/o branches
Compound – ducts w/ branches
Tubular – tubes
Acinus/alveolus – saclike
Endocrine gland (endo-within): glands w/o ducts

Hormones are secreted into blood
37
Exocrine Gland Structures
38
Exocrine Gland Structures
39
Connective Tissue
• The most abundant and widely distributed
tissue in the body
• Multiple types, appearances and
functions
• Relatively few cells in extracellular
matrix (think: fruit “cells” floating or
suspended in Jell-O)
• Protein fibers
• Ground substance
• Fluid
40
Structure of Connective Tissue
Three types of protein fibers:
 Collagen fibers:


Reticular fibers:


Rope-like; resist stretching
Fine, short collagen fibers; branched for
support
Elastic fibers:

Coiled; stretch and recoil to original shape
41
Structure of Connective Tissue,
continued…

Ground substance – combination of
proteins and other molecules


Varies from fluid to semisolid to solid
Proteoglycans – protein/polysaccharide
complex that traps water
42
Naming of Connective Tissue Cells

Based on function:



Blast (germ) – produce matrix
Cyte (cell) – cells maintain it
Clast (break) – cells break down for remodeling





Osteoblast (osteo-bone) – form bone
Osteocyte – maintain bone
Osteoclast – break down bone
Macrophage (makros-large + phago-to eat) – large,
mobile cells that ingest foreign substances found in
connective tissue
Mast Cells – nonmotile cells that release chemicals
that promote inflammation
43
Functions of Connective Tissue
1. Enclose organs and separate organs
and tissues from one another
• Liver, kidney; muscles, blood vessels,
nerves
2. Connect tissue to each other
• Tendons – muscles to bone
• Ligaments – bone to bone
3. Support and movement
• Bones, cartilage, joints
44
Functions of Connective Tissue,
continued…
4. Storage
• Fat stores energy; bone stores calcium
5. Cushion and insulation
• Fat cushions/protects/insulates (heat)
6. Transportation
• Blood transports gases, nutrients,
enzymes, hormones, immune cells
7. Protection
• Immune & blood cells protect against
toxins/tissue injury; bones protect
underlying structures
45
Classification of Connective Tissues
46
Loose connective tissue



Composition: ECM has
fibroblasts, other cells,
collagen, fluid-filled
spaces
Functions: forms thin
membranes between
organs and binds them
(loose packing material)
Locations: widely
distributed, between
glands, muscles, nerves,
attaches skin to tissues,
superficial layer of
dermis
47
Adipose Connective Tissue



Composition: very little
ECM (has collagen and
elastic fibers); large
adipocytes filled with lipid
Functions: Stores fat,
energy source, thermal
insulator, protection/
packing material
Locations: Beneath the
skin, in breasts, within
bones, in loose
connective tissues,
around organs (kidneys
and heart)
48
Dense Fibrous/Collagenous
Connective Tissue



Composition: ECM
mostly collagen (made
by fibroblasts),
orientation varies
Functions: withstands
pulling forces, resists
stretching in direction of
fibers orientation
Locations: tendons,
ligaments, dermis of
skin, organ capsules
49
50
Dense Elastic Connective Tissue



Composition: ECM
collagen and elastic
fibers; orientation
varies
Functions: stretches
and recoils; strength
in direction of fiber
orientation
Locations: arterial
walls, vertebral
ligaments, dorsal
neck, vocal cords
51
Cartilage

Chondrocytes (cartilage cells) inside lacunae
(small spaces)
 Matrix composition (ECM):




Collagen – flexibility & strength
Water (trapped by proteoglycans) – rigidity and
flexibility
No blood vessels – slow healing, can’t bring
cells/nutrients
Three types:



Hyaline cartilage
Elastic cartilage
Fibrocartilage
52
Types & Locations of Cartilage
53
Examples of Cartilage
54
Hyaline Cartilage



Composition: solid
matrix, small evenly
distributed collagen
fibers, transparent matrix,
chondrocytes in lacunae
Functions: supports
structures, some
flexibility, forms smooth
joint surfaces
Locations: costal
cartilages of ribs,
respiratory cartilage rings,
nasal cartilages, bone
ends, epiphyseal (growth)
plates, embryonic
skeleton
55
56
Fibrocartilage



Composition: similar to
hyaline, numerous
collagen fibrous
arranged in thick
bundles
Functions: somewhat
flexible, withstands
great pressure,
connects structures
under great pressure
Locations:
intervertebral disks,
pubic symphysis,
articulating cartilage of
some joints (knee, TMJ)
57
Elastic Cartilage

Composition: similar
to hyaline cartilage,
abundant elastic fibers
 Functions: rigidity,
more flexibility than
hyaline (elastic fibers
recoil to original
shape)
 Locations: external
ears, epiglottis,
auditory tubes
58
Bone



Composition: hard,
mineralized matrix,
osteocytes inside
lacunae, lamellae
layers
Functions: strength,
support, protects
organs,
muscle/ligament
attachments,
movement (joints)
Locations: all bones
of body
59
60
61
Blood



Composition: blood cells
in a fluid matrix (plasma)
Functions: transportation
(O2, CO2, hormones,
nutrients, waste, etc.),
protect from infection,
temperature regulation
Locations: in blood
vessels and heart,
produced by red bone
marrow, WBCs leave
blood vessels and enter
tissues
62
63
Muscle Tissue

General features:

Can contract




Contractile proteins
Enables movement of
the structures that are
attached to them
Muscle fibers = cells
Three (3) types of muscle
tissue:



skeletal
smooth
cardiac
64
Skeletal Muscle

Composition:
striated muscle
fibers, large,
cylindrical cells that
have many nuclei
near periphery
 Functions: body
movement,
voluntary control
 Locations:
attached to bone
65
Cardiac Muscle

Composition:
cylindrical cells,
striated, single
nucleus, branched
and connected with
intercalated disks
 Functions: pump
blood, involuntary
control
 Locations: heart
66
Smooth Muscle



Composition: cells
tapered at each end, not
striated, single nucleus
Functions: regulates
organ size, forces fluid
through tubes, regulates
amount of light entering
eye, “goose bumps”,
involuntary control
Locations: walls of hollow
organs and tubes
(stomach, intestine, blood
vessels), eye
67
Nervous Tissue

Forms brain, spinal cord, peripheral nerves
 Functions:







Conscious control of skeletal muscles
Unconscious control of cardiac muscles
Self and environmental awareness
Emotions
Reasoning skills
Memory
Action potentials = electrical signals responsible
for communication between neurons and other
cells
68
Nervous Tissue Structure

Neurons = conducts
action potentials (a.p.’s)




Cell body = contains
nucleus, site of general
cell functions
Dendrite = conduct a.p.’s
toward cell body
Axon = conducts a.p.’s
away from cell body
Neuroglia = support cells:
nourish, protect, insulate
neurons
69
70
Membranes
Thin sheet/layer of tissue covering a
structure or lining a cavity
 Made of epithelium & connective tissue
 Types:

Mucous membranes
 Serous membranes
 Skin/cutaneous membranes
 Synovial membranes
 Periosteum

71
Membranes
Mucous
Serous
Synovial
72
Mucous Membranes

Structure: various types of epithelia resting on a
thick layer of connective tissue
 Locations: line cavities that opening to outside of
body (digestive, respiratory, excretory,
reproductive tracts)
 Mucous glands secrete mucus
 Functions:



Protection – oral cavity (stratified squamous epithelium)
Absorption – intestine (simple columnar epithelium)
Secretion – mucus and digestive enzymes in intestine
73
Serous Membranes
Structure: simple squamous epithelium
resting on delicate layer of loose
connective tissue
 Locations: line trunk cavities, cover
organs
 Mucous glands secrete serous fluid onto
membrane surface
 Function: prevent damage from abrasion
between organs in thoracic and
abdominopelvic cavities

74
Types of Serous Membranes

Pleural membranes – lungs


Pericardial membranes – heart


Pleurisy – inflammation of pleural
membranes
Pericarditis – inflammation of pericardium
Peritoneal membranes – abdominopelvic

Peritonitis – inflammation of peritoneum
75
More Serous Membranes

Skin/cutaneous
membranes



Synovial membranes



Stratified squamous
epithelium & dense
connective tissue
Skin
Connective tissue
Line joint cavities
Periosteum


Connective tissue
Surrounds bone
76
Inflammation

In response to tissue damage
Viral/bacterial infections
 Trauma


Functions:
Mobilize body’s defenses
 Destroy microorganisms, foreign materials,
damaged cells
 “Pave way” for tissue repair

77
Symptoms of Inflammation
Redness
 Heat
 Swelling
 Pain
 Disturbance of function

* Inflammation is beneficial, though painful!
78
Inflammatory Response

Mediators of inflammation cause dilation 
permeability of blood vessels (redness/heat)






Bring blood and important substances to site
Edema = swelling (water, proteins, etc.) of
tissues
Fibrin = protein that “walls off” site; keeps
infection from spreading
Neutrophils ingest bacteria (phagocytic WBC)
Macrophage ingest tissue debris
Pus = mixture of dead neutrophils, cells, fluid
79
Inflammation is
adaptive:

Inflammation warns
person from further injury:



Pain
Limitation of movement
(edema)
Tissue destruction
 Fibroclast migrate to
damaged tissue and
digest
80
Tissue Repair

Substitution of viable cells for dead cells
Regeneration = same type of cells takes
place of previous cells; same function
 Replacement = different type of tissue
develops; forms scars; loss of some
function
 Fibroclast lays down fibrin and forms scar
tissue
 Type of tissue repair is determined by:

Wound severity
 Tissue types involved

81
Not all cells divide alike…

Labile cells (not fixed)



Stable cells



Divide continuously through life
Skin, mucous membranes
Don’t actively divide, but can after injury
Connective tissue, glands (liver, pancreas)
Permanent cells


Little to no ability to divide
Neurons, skeletal muscle


If killed, replaced by connective tissue
Recover from limited damage (axon of neuron)
82
Review steps of tissue repair:
1.
2.
3.
4.
5.
6.
7.
8.
Clot (fibrin)
Scab (seal)
Blood vessel
dilation
Fibroclast-clean
up
Fibrin “walls off”
Epithelium
replaced
Scab sloughs
Fibroblasts form
granulation
tissue
Wound
contracture
83
It’s tough getting old…

Tissue changes with age:







 neurons and  muscle cells
 visual acuity, smell, taste, touch
 in functional capacities of respiratory and
cardiovascular systems
Slower cell division means slower healing
 flexibility (irregular collagen fibers in tendons &
ligaments)
 elasticity (elastic fibers bind to Ca2+, becoming
brittle) – makes skin wrinkled too 
Atherosclerosis – plaques in blood vessels
84
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