Download 2401_ch4.pdf

Chapter 4
Histology – The Study of Tissues
Please note: there are lots of images in this lecture that are not available
for download with this presentation due to copyright limitations
1
Histology
The study of tissues…
Four major tissue types in the body
¾ Epithelial tissue (epithelium)
¾ Connective tissue
¾ Muscle tissue
¾ Nerve tissue
2
Characteristics of Epithelium
¾Cells with little extracellular matrix between individual cells
¾Functions include cover/line surfaces, forms glands
¾Most are attached at a basal surface and exposed at a free surface
¾Basal surface often attached at basement membrane
¾Specialized connections/contacts between cells
¾Capable of division (by mitosis) so can replace damaged cells – useful for
cells that line surfaces
¾Nutrients reach these cells only through diffusion across basement
membrane.
3
1
basement membrane is non-cellular
it is secreted by the epithelial cells
4 present in all epithelium
not
Types of Epithelium
How classified & named:
¾ by cell shape
9 squamous = flat
9 cuboidal = cube shaped
9 columnar = tall & rectangular
¾ By number of layers
9 simple = single layer of cells
9 stratified = multiple layers of cells
9 pseudostratified = single layer that ‘appears’ multi-layered
5
Types of Epithelium
6
2
Simple Squamous Epithelium
Locations - lining of blood & lymph vessels, in alveoli
of lungs, in kidney tubules (in loop of Henle), and
serous membranes
Appearance resembles a ‘field of fried eggs’
Functions include protection against friction, diffusion,
filtration, secretion & absorption
7
8
Simple Cuboidal Epithelium
Locations - kidney tubules, glands, gland ducts, choroid
plexus of brain, bronchioles of lungs, ovary surfaces
Appearance – a single layer of cube-like cells,
approximately as wide as tall. May have microvilli (for
absorption) or cilia (to move mucus over the surface of
the cells)
Functions – secretion & absorption in kidney, produce
glandular secretions, produce cerebrospinal fluid, move
mucus
9
3
10
Simple Columnar Epithelium
Locations – glands & (some) ducts, ventricles of brain,
bronchioles, ear ‘tubes’, uterine lining, fallopian tube
lining, stomach, intestine, gall bladder, bile duct
Appearance – tall rectangular cells in single layer. May
have microvilli for absorption, or cilia to create a
current over the surface of cell layer. May have Goblet
Cells (specialized columnar cells) which produce
secretions.
Functions – move particles across cell surface,
absorption (intestinal cells), secretion (by goblet cells)
11
12
4
Stratified Squamous Epithelium
Two Types of StSE located by type:
¾ Keratinized StSE– surface of skin
¾ Moist StSE – linings of mouth, throat, esophagus, anus, vagina,
urethra & cornea of eye
Appearance – several layers of cuboidal cells with cells
becoming flattened toward the upper layers. Moist
StSE retains cytoplasm in upper layer cells. Keratinized
StSE cells contain keratin (tough protein) rather than
cytoplasm
Function – protects against abrasion & infectious
organisms
13
14
Stratified Cuboidal Epithelium
Locations – ducts of salivary glands & sweat glands,
ovarian follicles
Appearance - several layers of cube-like cells (height
approximately equal to width)
Functions – secretion, absorption, barrier against
infectious organisms.
15
5
16
Stratified Columnar Epithelium
Locations – duct of mamary gland, larynx, urethra of
male.
Appearance – upper layer(s) columnar (taller than
wide) with lower layers becoming progressively shorter.
Lower levels of cells appear cuboidal.
Functions – secretion, protection against infectious
organisms.
17
18
6
Pseudostratified Ciliated
Columnar Epithelium
Locations – lining nasal cavity & sinuses, auditory
tubes, pharynx, trachea & bronchi
Appearance – all cells contact basement layer. Some
reach free border while some do not. This places nuclei
at several levels and gives appearance of multiple layers
of cells
Functions – produce & secrete mucus onto free surface
(glandular function). Move mucus with cilia to clean
foreign particles from cell surfaces.
19
20
Transitional Epithelium
Locations - lining of ureters (tube draining kidney),
urinary bladder & upper urethra
Appearance – multiple layers – cuboidal when relaxed
and squamous when stretched
Function – allow wall of bladder (& these tubes) to
stretch. Protects underlying tissues from urine
21
7
22
Some Details About Epithelium
Surfaces types
¾ smooth – provides reduced friction surface
¾ microvilli – increase surface area & aid absorption
¾ cilia – move materials such as mucus across cell surfaces
Varied cell-to-cell connections along sides and base of cells
¾ hold cells together
¾ create a permeable barrier
¾ provide for cell-to-cell communication
23
24
8
Cell-to-Cell Connections
Desmosome – a glycoprotein (carbohydrate/protein)
linkage providing a very strong connection for cells in
high stress regions (e.g. skin)
Hemidesmosomes – bind bottom-most cells to the
basement layer in high stress areas
Gap Junction – small protein channel (pore) that
allows ions and small molecules to flow between cells
(communication)
Tight Junction – barrier to permeability. Large
molecules can not pass except through transport
proteins. Not as strong as desmosomes. Includes:
25
¾ zonula adherens – between cell membrane (‘glue’)
¾ zonulaa occludens – overlapping of cell membranes
26
Glands
Designed to secrete some cellular product
Most glands are primarily epithelial tissue supported by
connective tissue
Glands can be:
¾ Exocrine – glands with ducts or
¾ Endocrine – glands without a duct
May be
Multicellular – many cells
Unicellular – single cell (e.g. Goblet Cells)
Simple – ducts with few branches
Compound – ducts with many branches
27
9
Classifying Glands continued
Classified by shape - Glands ducts may end in:
¾ acini – saclike tubes or
¾ alveoli – grapelike clusters
Classification by how gland products leave cell:
¾ Merocrine – product leaves by exocytosis or active transport –
No loss of actual cellular material (e.g. ‘watery’ sweat glands)
¾ Apocrine - portions of cells shed and become part of secretion.
(e.g. mammary gland)
¾ Holocrine – entire cells rupture and become part of secretion
(e.g. sebaceous/oil glands in skin)
28
29
30
10
Merocrine
Apocrine
Holocrine
31
Connective Tissues
Classification based not only on cell types but also on
what type of nonliving extracellular matrix found
between the cells
Types of extracellular matrix include
¾ protein fibers (with little or no ‘ground material’)
¾ protein fibers plus ‘ground material’
32
Cell Types in Connective Tissues
Cells named (prefix) based on tissue type
¾ Cartilage cells: prefix = chondro¾ Bone cells: prefix = osteo-
Cells named (suffix) based on function
¾ -cyte – these are maintenance cells, do the ‘normal job of tissue
¾ -blast = these cells create the extracellular matrix (produce
fibers, lay down ‘ground material’, etc.
¾ -clast = these cells break down tissue for remodeling
Thought questions:
¾ What job would a fibroblast have?
¾ What about an osteoclast?
33
11
Types of Protein Fibers
Collagen
¾ rope-like fibers very strong NOT elastic (stretchy)
¾ strengthen tissues
Reticular (reticulum = “net”)
¾ short, thin fibers that branch and form a network of supporting
fibers.
¾ Fill spaces in tissues & organs
Elastin
¾ spring-like fibers often seen in large interwoven networks
¾ stretchy, provide resilience and elasticity to tissues
34
Matrix
Matrix is non-fibrous material between the cells
Some types seen include:
Hyaluronic acid – an unbranched polysaccharide chain
¾ very good lubricant, found in joint cavities and in the eye
Proteoglycan – a proteoglycan is sugars attached to a
protein core resembling a pine tree
¾ Proteoglycans retain water in their folds, functioning somewhat
like sponges.
¾ Give tissues some flexibility to return to original shape when
squashed or deformed
35
Fibrous Connective Tissues
Protein fibers make up much of the extracellular space
(space between the cells)
¾ Two subtypes, classified by amount of fibers in tissue
Loose Connective Tissue (a.k.a. Areolar Connective Tissue)
¾ Loose has relatively few fibers arranged in networks and has lots
of fluid filling the spaces between cells
¾ serves as ‘packing/padding’ material in many organs
Dense Connective Tissue
¾ Densely packed bundles of fibers fill much of the extracellular
space
¾ connecting structures, and support structures
¾ may be regular or irregular (more on this in a moment)
36
12
Loose (Areolar) Connective Tissue
Found throughout the body. Attaches skin to underlying muscle.
Much of the body's epithelium rests on areolar tissue
Individual cells (fibroblasts) located within a loose network of
collagen fibers (strength) and elastic fibers (flexibility &
elasticity)
Provides support, packing & nourishment – remember that no
blood vessels penetrate into epithelium. The epithelial cells that
rest on areolar tissues get their nourishment from blood vessels
ending here!
37
38
Dense Regular Connective Tissue
Sometimes known as Dense White Fibrous Connective Tissue
Tendons & Ligaments are made of DRCT
mostly collagen fibers with the grain of fibers running in similar
direction (sometimes wavy, but fibers still parallel each other)
Attach bone to bone (ligament) or muscle to bone (tendon)
provide great strength. These fibers resist stretching (not very
flexible)
39
13
40
Dense Regular Elastic
short ligaments connecting
vertebrae & vocal cords
Composed of a mixture of
collagen and elastic fibers
all oriented in the same
direction (similar ‘grain’)
These large bundles of tissue
are both strong and flexible.
Stretch and snap back along
their length, in the direction
41 of the fibers.
Dense Irregular Elastic
wall of large elastic arteries
(e.g. aorta)
Composed of a mixture of
collagen and elastic fibers
These large bundles of tissue
are both strong and flexible.
42
14
Dense Irregular Collagenous
the ‘leather’ or dermis of the skin, outer coverings of
blood vessels and other tubes in the body, protective
coverings around organs
Layers of collagen fibers that run in several directions
Very strong, protective coverings that resist stretching
in several directions.
43
44
Adipose (fat) Tissue
Subcutaneous (under the skin), around kidneys, in breast tissue,
interspersed in the loose connective tissue filling body spaces
Primarily cells with few fibers or other extracellular material
between the cells. Adipocytes (fat cells) contain enormous
amounts of lipid. Thin layer of cytoplasm is pushed to the edge
of the cell by the fat stored in these cells.
Several functions include, energy storage, packing/padding
material to protect internal organs, insulation against heat loss,
buoyancy in water dwelling creatures (or swimming humans)
45
15
46
Reticular Tissue
Located in lymph nodes, spleen and bone marrow
This is characterized by an irregular network of fibers
Provide support & reinforcement for delicate structures
lymph nodes and the hemopoietic (blood producing)
tissues inside bone.
47
48
16
Bone Marrow
At this point your book introduces the rather involved topic of bone marrow
Bone marrow actually has two major types, Red & Yellow
Red bone marrow consists of reticular tissue, which we have just discussed,
supporting blood forming cells which are responsible for making new blood
cells
Yellow bone marrow is mostly fat (adipose tissue) and is used for energy
storage
As you can see, bone marrow has several function and several of the tissue
types we are discussing…
49
50
Cartilage
Several types include:
¾ Hyaline
¾ Elastic Cartilage
¾ Fibrocartilage
51
17
Hyaline Cartilage
Located at growth plates of growing bones, joints of long bones,
ends of ribs near sternum, tip of nose, trachea and other places
Small collagen fibers spread throughout the matrix
Chondrocytes (cartilage cells) live in small holes called lacunae
(singular = lacuna) in the matrix.
matrix is firm and ‘glossy’ gives strength & flexibility, in joints it
provides a smooth, flexible articulating surface
52
53
Fibrocartilage
outer covering of intervertebral disks, pubic symphysis,
some joints
collagen fibers in large bundles (fibers are more
numerous than in other cartilage types)
lightly flexible but very strong. Attaches structures that
are subject to large stresses on a regular basis
54
18
55
Elastic Cartilage
Outer ear and auditory tube, epiglottis
Similar to hyaline but contains elastin fibers as well as
collagen
rigid but more flexible support
56
57
19
58
Bone
Hard connective tissue, partly organic, partly inorganic
Organic components include:
cells in lacunae (osteocytes – osteoclasts & osteoblasts)
fibers – primarily collagen
Inorganic components include:
hydroxyapatite (calcium & phosphate)
Two types of bone
¾ Cancellous (spongy) bone – hard supporting with spaces between
¾ Compact bone – densely packed bony layers with little space
59
Cancellous Bone
sometimes called ‘spongy’ due to appearance
Found in the interior of bones in several locations including:
skull (flat bones), vertebrae, sternum, pelvis, ends of long bones
Lacy network of supporting layers of bone with large spaces between…
Spaces usually filled with hemopoietic (stem cell) tissues which make
new blood cells
Reduce weight of bone, provide support & protection for hemopoietic
tissues
60
20
Cancellous “Spongy” Bone
61
Compact Bone
Outer part of bones & shaft of long bones
Hard bony matrix (hydroxyapatite) makes up most of
the material
osteocytes located in lacunae arranged in circular
patterns (like multiple planets in orbit)
Provides enormous strength to the bone
62
Blood
yes, it’s a connective tissue…
Matrix is mostly liquid. Cells move freely in the matrix
Two primary types of cells
Red Blood Cells
White Blood Cells - many different types: discussed in
Ch 19
63
21
64
Red cells, white cells, platelets
Relative size of RBC on tip of
small gauge hypodermic needle
65
Note ‘biconcave disk’ shape
of Red Blood Cells
End of Connective Tissue
66
22
Muscle
Electrically excitable tissue – capable of contraction
Structurally can be either smooth or striated (striped)
functionally can be either voluntary or involuntary
Three types include:
Skeletal (striated) – most of your muscle mass, largely
voluntary
Cardiac (striated) – heart muscle, largely involuntary
67Smooth - involuntary
Skeletal Muscle
Attaches bone to bone
Appear striped/banded, long cylindrical cells are multinucleate
(have many nuclei). Nuclei near periphery of cell
Function: move body parts - voluntary
68
Cardiac Muscle
Heart Muscle
Cylindrical & branched with
nuclei near center of cylinder.
Cells join each other at
specialized structures known as
intercalated disks
Function = heart contraction, for
pumping. Involuntary control
(some minor levels of conscious
control through relaxation)
69
23
Smooth Muscle
walls of digestive system,
walls of blood vessels, eye,
skin
Cylinders tapered at both ends
& are not striated. Cells have a
single, central nucleus.
Function – expand & contract
tubes (digestive & blood
vessels), regulate size of pupil
in eye, ‘goose bumps’ of skin
70
Nervous Tissue
Electrically Active Tissue (as was muscle)
Major cell types:
¾ Neurons - ‘nerve cells’
¾ Neuroglia (or Glia) – support cells
71
72
24
Multipolar Neuron
Called multipolar (many poles) because the cell body
has several processes entering or leaving.
Found in brain, spinal cord, & ganglia
Parts include dendrites, cell body & a single (usually)
axon
(book discusses glial sheath around the cell, this is
technically NOT part of the neuron proper but is a
separate support cell)
73
74
Pseudounipolar Neuron
Cell body has a single process (axon) leaving the cell.
Found in ganglia (clusters of neuron cell bodies) outside
the brain & spinal cord.
Bring information about the body or environment back
to the brain or spinal cord.
75
25
76
True Unipolar neurons occur in developing (Fetal) brains
77
Unipolar Neuron – Axon
(note absence of dendrites)
Bipolar Neuron
Cell body has two processes,
one dendrite entering and one
axon leaving the cell.
Found in special sense organs
such as the eye
Bring sensory information to
the brain.
78
26
Neuroglia
Support cells found on and around neurons
Many types providing several types of services for
neurons
some services include:
providing nourishment
insulate (like wire insulation)
protection
isolate from potentially harmful substances (blood brain
barrier)
79
Embryonic Tissues
Tissues present early in development during which produce
specific tissues & organ systems
Endoderm (inner layer) – forms digestive tract
Mesoderm (middle layer) – forms muscle, bone, blood vessels
Ectoderm (outer layer) – forms skin & nervous system
(neuroectoderm)
Neural Crest Cells (portion of neuroectoderm) forms peripheral
nerves, some of face & skin pigment
Mesenchyme – forms connective tissues
80
Readings
Please read section on
Membrane structure & function
81
27
Inflammation & Tissue Repair
an example of how the tissue types interact
to repair damage
82
83
84
28
85
what is dermis?
29