Transcript Tissue: The Living Fabric

Tissue: The Living
Fabric
Chapter 4
4 Types of Tissues
Epithelial (covering)
 Connective (support)
 Muscle (movement)
 Nervous (control)
Histology - study of tissues
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I. Epithelial Tissue p. 99
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Sheet of cells that covers a body surface
or lines a body cavity
1. Covering & lining epithelium
2. Glandular epithelium
A. Special Characteristics
1.
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3.
4.
5.
6.
Cellularity
Specialized Contacts
Polarity (apical & basal surfaces) microvilli, cilia, basal lamina
Supported by Connective Tissue reticular lamina, basement membrane
Avascular, but Innervated
Regeneration
B. Classification
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2 Names:
1st Name - How many layers of cells.
2nd Name - Shape of cells.
Simple vs. Stratified
Squamous vs. cuboidal vs. columnar
Nucleus shape conforms to cell.
Look at fig. 4.1 p. 100
1. Simple Epithelia p. 101
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Most concerned with absorption,
secretion, and filtration.
Simple Squamous Epithelium
Thin and permeable - filtration or exchange of
substances by rapid diffusion
 Found in places like the kidney filtration
membrane, lung air sacs, capillaries, serous
membranes
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Simple Cuboidal Epithelium
Secretion and absorption
 Common in kidney tubules and glands
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Simple Columnar Epithelium
Absorption and secretion
 Lines digestive tract
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Dense microvilli
Goblet cells - secrete mucus
Sometimes cilia
Pseudostratified Columnar Epithelium
Vary in height, so it appears that there is more
than one layer
 Secretion and absorption - ciliated version
containing goblet cells lines respiratory tract
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Fig. 4.2 p. 101-103
2. Stratified Epithelia p. 105
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2 or more layers, regenerate from below
More durable than simple epithelia Protection
Stratified Squamous Epithelium
Most widespread, thick
 Free surface cells are squamous, deeper are
cuboidal or columnar, constant regeneration
 External part of skin - keratinized
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Stratified Columnar Epithelium
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Rare, large ducts of some glands
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Transitional Epithelium
Lining of urinary organs,
subjected to stretching when filled
with urine
Cells change shape when
stretched
Fig. 4.2 p. 104-105
3. Glandular Epithelia p. 106
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Gland - one or more cells that make &
secrete (export) a particular product
(secretion)
Secretion is aqueous & usually contains
proteins
Classified based on:
1.
2.
Endocrine or Exocrine
Unicellular or Multicellular
a. Endocrine Glands
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Release their product into the extracellular
space
Often ductless
Produce hormones - targeted to specific
organ(s)
Most are compact multicellular organs, but
some are individual cells (diffuse
endocrine system)
We will deal more with this in Chp. 15
b. Exocrine Glands
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More numerous than endocrine glands
Secrete onto body surfaces (skin) or into
body cavities
Single or multicelled
Examples: mucous, sweat, oil, salivary,
liver, pancreas
Unicellular - goblet cell - produce mucin
(becomes mucus)
b. Exocrine Glands cont’d
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Multicellular
2 parts: duct & secretory unit
 Supportive connective tissue surrounds the
secretory unit, often forming a fibrous capsule that
extends into the gland, dividing it into lobes
 Simple or Compound
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Simple - single unbranched duct
Compound - branched duct
Also categorized by secretory units:
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Tubular - form tubes
Alveolar (acinar) - form small sacs
Tubuloalveolar - contain both
Multicellular cont’d
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Different modes of secretion:
Merocrine glands - secrete products by exocytosis
examples: pancreas, most sweat glands, &
salivary glands
 Holocrine glands - accumulate products within the
cells until they rupture - cells are replaced by
division of lower cells - example: sebaceous (oil)
glands of the skin
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Fig. 4.4&4.5, p. 107-108
II. Connective Tissue p. 108
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Most abundant and widely distributed
of the primary tissues
4 main classes: (fig. 4.6 p. 109)
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Connective tissue proper, cartilage,
bone, and blood
4 major functions:
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Binding & support, protection,
insulation, and transportation
A. Common Characteristics
1.
2.
3.
4.
Common origin - from mesenchyme
Degrees of vascularity - wide range
Extracellular matrix - mostly composed of
this matrix, few cells
--> This allows it to withstand a lot of
physical stress and abuse
B. Structural Elements p. 109
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3 main elements:
Ground substance
 Fibers
 Cells
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Ground substance and fibers make up the
extracellular matrix
Wide variety within connective tissues, but
areolar connective tissue is used as a
prototype or model (fig. 4.7 p. 110)
1. Ground Substance p. 109
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Unstructured material that fills the space
between cells, contains fibers
Composed of interstitial fluid, cell adhesion
proteins, and proteoglycans
Holds large amounts of fluid
Functions as a molecular sieve, or
medium, through which nutrients and other
dissolved substances can diffuse between
the capillaries and the cells
2. Fibers p. 110
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Provide support
3 Types:
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Collagen Fibers: made of collagen protein, very tough
(stronger than steel), thick, white fibers
Elastic Fibers: made of elastin protein, long & thin,
rebound tissue when stretched, yellow fibers, found in
skin, lungs, blood vessels
Reticular Fibers: made of collagen protein, thin, form
delicate networks, found in small blood vessels &
basement membrane of epithelial tissues
3. Cells p. 111
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Each class has its own fundamental cell
type: -blast indicates undifferentiated
cells
Fibroblast - connective tissue proper
2. Chondroblast - cartilage
3. Osteoblast - bone
4. Hematopoietic stem cell - blood
Once these cells synthesize the matrix, they
become mature, -cyte is added to name
1.
3. Cells cont’d
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Accessory cells: fat cells, white blood
cells, mast cells, macrophages, plasma
cells
Mast cells: cluster along blood vessels,
detect foreign substances & initiate
inflammatory response (release histamine)
Macrophages: phagocytize foreign
materials & dead tissue cells, part of
immune system
C. Types of Connective
Tissue p. 112-119
Embryonic connective tissue:
Mesenchyme
1.
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first definitive tissue formed
Arises during the early weeks of embryonic
development and eventually differentiates
into all other connective tissues
2. Connective tissue proper
Loose connective tissue, p. 111
a)
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Areolar connective tissue - “universal
packing material between other tissues,” has
all 3 fiber types
Adipose (fat) tissue - similar to areolar but
has greater nutrient-storing ability, cells are
adipocytes
Reticular connective tissue - only reticular
fibers, lymph nodes, spleen, bone marrow
Dense Connective Tissue
b)
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Dense regular connective tissue - variety of
dense tissues, mostly made up of fibers,
also called fibrous connective tissues, poorly
vascularized, forms tendons, ligaments
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Some have more elastic fibers (ex. Ligaments of
vertebrae) and are called elastic connective
tissue
Dense irregular connective tissue - similar to
last type, but collagen fibers are thicker and
are arranged irregularly, found in dermis,
joint capsules
3. Cartilage p. 116
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Stands up to both tension and compression,
characteristics intermediate between dense
connective tissue and bone
Avascular and lacks nerve fibers
Contains up to 80% water, Chondrocytes are
the primary cell
3 types of cartilage:
1.
Hyaline: most abundant, lots of collagen, examples:
articular cartilage, tip of nose, connect ribs to
sternum, respiratory system passages, embryonic
skeleton, epiphyseal plates
3 types of Cartilage con’t
2.
3.
Elastic Cartilage: similar to hyaline, but
with more elastin fibers, examples:
external ear, epiglottis
Fibrocartilage: often found where hyaline
meets a true ligament or tendon,
examples: intervertebral discs, menisci of
knee
4. Bone p. 118
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Also known as osseous tissue
Supports and protects body tissues, stores
fat, and synthesizes blood cells
Matrix is similar to cartilage but harder,
because of inorganic calcium salts
Well supplied by blood vessels
More on bone in ch. 6
5. Blood p. 118
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Does not connect things or give support
But it does come from mesenchyme and
has blood cells surrounded by a fluid
matrix (blood plasma)
The fibers of blood are only visible during
clotting
Transport system in the body
We will deal more with blood in ch. 16
III. Epithelial Membranes:
Coverings and Linings p. 118
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Incorporate both epithelial and connective
tissues
“A continuous multicellular sheet
composed of at least 2 primary tissue
types: an epithelium bound to an
underlying layer of connective tissue
proper,” so they are simple organs
3 types: cutaneous, mucous, & serous
Fig. 4.9 p. 120
A. Cutaneous Membrane p.
120
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Skin, consists of keratinized stratified
squamous epithelium (epidermis) attached
to a thick layer of dense irregular
connective tissue (dermis)
Dry membrane (exposed to air)
Ch. 5 for more with this organ system
B. Mucous Membrane p. 121
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Line body cavities that open to the exterior
- i.e. digestive, respiratory, & urogenital
tracts
Wet membranes
Most have stratified squamous or simple
columnar epithelia over a layer of loose
connective tissue, which sometimes lays
on a third layer of smooth muscle cells
Often for absorption and secretion
C. Serous Membrane p. 121
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Wet membranes found in closed ventral body
cavities
Consists of simple squamous epithelium
(mesothelium) resting on a thin layer of loose
connective (areolar) tissue
Has serous fluid that lubricates moving organs
Named for the organs they surround: pleura =
lungs; pericardium = heart; peritoneums =
organs of abdominopelvic cavity
IV. Nervous Tissue p. 121
Main parts of nervous system –
brain, spinal cord, and nerves
 2 major cell types:
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Neurons - generate and conduct nerve
impulses
 Supporting cells - support, insulate, and
protect the neurons
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Fig. 4.10 p. 121
More in Ch. 11
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V. Muscle Tissue p. 122
Highly cellular, well-vascularized,
responsible for movement
 Myofilaments: actin and myosin protein
fibers that are responsible for contraction
3 Types:
A. Skeletal - attached to bones, muscle
fibers (cells) are long with many nuclei,
striated, voluntary (chp. 9)
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V. Muscle Tissue con’t
B.
C.
Cardiac - found only in heart, pumps
blood, striated, uninucleate, involuntary,
branching cells that connect at
intercalated discs (an area with a lot of
gap junctions),
ch. 17
Smooth - no striations, spindle shaped
uninucleate cells, found in hollow organs
(ex. Digestive, urinary, uterus, blood
vessels), involuntary
ch. 9
Fig. 4.11, p. 122-123
VI. Tissue Repair p. 122
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The body has several defense
mechanisms for preventing injury and
infection - when these are penetrated, the
inflammatory and immune responses are
triggered to get rid of infection.
The tissue then must be repaired.
A. Steps, p. 124
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Occurs in 2 major ways, which depend on the
type of tissue damaged and the severity of the
injury
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Regeneration - replacement of tissue with the same
kind of tissue
Fibrosis - replacement of tissue with fibrous
connective tissue (scar tissue)
Step 1: Inflammation sets the stage.
Step 2: Organization restores the blood supply.
Step 3: Regeneration and fibrosis effect
permanent repair.
B. Homeostatic Imbalance p.
125
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During the healing process, tissues which
cannot regenerate very well produce a
large amount of scar tissue, which is not
as flexible as the original tissue.
It also causes some shrinking in the
tissue. This can be serious in organs like
the heart, where it reduces capacity and
function. Internal organs can also get
stuck together during healing, causing
dysfunction & pain.