Download Lecture 4b - Connective tissues

Connective Tissue and
More
What is connective tissue?
Connective tissues, nervous, and
muscle tissues
Connective Tissue
Connective tissues
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Represent the most abundant by weight and
most widely distributed type of tissue in the
body
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Generally:
Bind structures together
Fill spaces in the body
Examples: Connective tissue proper,
Cartilage, Bone, Blood
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Figure 4.6
Connective Tissues –
general functions
Characteristics of
Connective Tissues
Connect epithelium to the rest of the
body (basal lamina)
z Have no contact with environment
(usually covered by epithelium)
z Usually highly vascular (good blood
supply)
z Also:
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Protect delicate organs
Provide structure and support (bone)
Insulate and store energy (fat)
Transport materials (blood)
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Specialized cells
Solid extracellular protein fibers
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Fluid extracellular ground substance
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Collagen, elastic, and reticular
unstructured material that fills the space between
cells
These latter two extracellular features are
called Matrix
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The Matrix
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The extracellular components of connective
tissues (fibers and ground substance):
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Matrix: ground substance
Makes up the majority of tissue volume
Determines specialized function:
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connective tissue proper Æ syrupy liquid
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Fills the spaces between cells and fibers
Functions as a molecular sieve through which
nutrients diffuse between blood capillaries and cells
Composed of
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cartilage Æ gel-like matrix
blood Æ fluid matrix
bone Æ crystalline solid
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Ground Substance:
Proteoglycan Structure
interstitial fluid
Cell adhesion proteins: serve as glue for cells to attach to
matrix
Proteoglycans: consist of a protein core with
glycosaminoglycans (GAGs) such as chondroitin sulfate
and hyaluronic acid which trap water and determine the
consistency
Matrix: Protein Fibers
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Collagen – tough but inelastic; provides very
high tensile strength (greater than steel)
Elastic – long, thin fibers that allow for
stretch; composed of elastin which is similar
to collagen
Reticular – branched collagenous fibers that
form delicate networks, resist force in many
directions
Figure 4.7
Elastic fibers allow a tissue to
stretch
Cells
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Fibroblasts – connective tissue proper
Chondroblasts – cartilage
Osteoblasts – bone
Hematopoietic stem cells – blood
White blood cells, plasma cells,
macrophages, and mast cells
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Other CTP cell types
Fibroblasts
Melanocytes
z Adipocytes – fat cells; insulation, energy,
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padding
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Stationary in the tissue
Secrete the protein fibers and ground
substance found in the matrix
Mesenchymal cells – stem cells; can
differentiate into other mesodermal cell types
Classification of
Connective Tissues
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Connective tissue proper:
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Fluid connective tissues:
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Supporting connective tissues:
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connect and protect
transport
structural strength
Connective tissue proper
(CTP)
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Classification of connective
tissues
Contains many types of cells and
extracellular fibers in a syrupy ground
substance
Look at the cell types and the number and
types of fibers to identify the type of tissue
Categories of
Connective Tissue Proper
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Loose connective tissue:
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more ground substance, less fibers
e.g., fat (adipose tissue)
Dense connective tissue:
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more fibers, less ground substance
e.g., tendons
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CTP: 3 types of Loose
Connective Tissues Proper
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Connective Tissue: Embryonic
The “packing materials” of the body
Packing material, fills spaces
Contains mesenchyme cells – leftover from
development, can differentiate into many of
the other resident cell types
3 types in adults:
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Mesenchyme – embryonic connective tissue
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Gel-like ground substance with fibers and starshaped mesenchymal cells
Gives rise to all other connective tissues
Found in the embryo
areolar
adipose
reticular
Areolar Connective Tissue
Model
Loose CTP #1: Areolar
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Areolar connective tissue
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Least specialized, open framework
Viscous ground substance with all three
connective tissue fibers
Fibroblasts, macrophages, mast cells, and some
white blood cells
Wraps and cushions organs
Widely distributed throughout the body
Separates skin from deeper tissues
Holds blood vessels and capillary beds:
Figure 4.8
Loose CTP #1: Areolar
Loose CTP #2: Adipose
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Adipose connective tissue
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Matrix similar to areolar connective tissue with
closely packed adipocytes
Reserves food stores, insulates against heat loss,
and supports and protects
Found under skin, around kidneys, within
abdomen, and in breasts
Local fat deposits serve nutrient needs of highly
active organs
Figure 4.9a
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Loose CTP #2: Adipose
Loose CTP #2: Adipose
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Contains many adipocytes (fat cells)
Figure 4–10a
Figure 4.9b
Adipose Cells
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Adipocytes in adults do not divide:
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Loose CTP #3: Reticular
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expand to store fat
shrink as fats are released
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Mesenchymal cells divide and differentiate:
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Reticular connective tissue
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to produce more fat cells
when more storage is needed
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Loose ground substance with reticular fibers
Reticular cells lie in a fiber network
Forms a soft internal skeleton, or stroma, that
supports other cell types
Found in Reticular organs: lymph nodes, bone
marrow, liver, and the spleen
Loose CTP #3: Reticular
Loose CTP #3: Reticular
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Figure 4.9c
Provides support
Figure 4–10b
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CTP: 3 Types of Dense
Connective Tissues
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Dense CTP #1: Dense Regular
Connective tissues proper
Tightly packed with high numbers of collagen
or elastic fibers:
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Dense Regular Connective Tissue
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dense regular connective tissue
dense irregular connective tissue
elastic tissue
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Parallel collagen fibers with a few elastic fibers
Major cell type is fibroblasts
Attaches muscles to bone or to other muscles,
and bone to bone
Found in tendons, ligaments, and aponeuroses
Dense CT #1: Dense Regular
Dense CTP #1: Dense Regular
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e.g. tendons, ligaments
Attachment and stabilization
Figure 4.9d
Dense CTP #2: Dense Irregular
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Dense CTP #2: Dense Irregular
Dense Irregular Connective Tissue
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Irregularly arranged collagen fibers with some
elastic fibers
Major cell type is fibroblasts
Withstands tension in many directions providing
structural strength
Found in the dermis, periosteum, perichondrium,
submucosa of the digestive tract, and fibrous
organ capsules
Figure 4.9e
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Dense CT #2: Dense Irregular
Dense CT #3: Elastic Tissue
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Made of mostly elastic fibers (elastin):
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e.g., elastic ligaments of spinal vertebrae
Figure 4–11c
Dense CT #3: Elastic Tissue
Fluid Connective Tissues
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Fluid connective tissues:
blood and lymph
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Fluid CT: Blood
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Formed elements
Formed elements are the cells plus the
platelets (which aren’t technically cells) =
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Red blood cells (erythrocytes) = majority
White blood cells (leukocytes)
Platelets
watery matrix of dissolved proteins
carry specific cell types (formed elements)
Connective Tissue: Blood
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Red and white cells in a fluid matrix (plasma)
Contained within blood vessels
Functions in the transport of respiratory
gases, nutrients, and wastes
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Fluid Elements of Blood
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Connective Tissue: Blood
Extracellular:
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Plasma – fluid portion of blood
Interstitial fluid – squeezed out of capillaries
Lymph – Int. fluid entering lymph vessels
Figure 4.9j
Flow of body fluids – A Cycle
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Supporting
Connective Tissues
Plasma in blood (without formed elements)
squeezes out of capillaries due to blood
pressure and small spaces between some
epithelial cells
Now in tissue spaces it is called interstitial
fluid. Passively enters lymphatic system.
Now it is called lymph. Returns to blood
through subclavian veins then to heart
Cycle repeats
What do supporting
connective tissues do?
Bone and Cartilage
Supportive Connective
Tissues
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Function: Support soft tissues and body
weight
Types:
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cartilage:
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gel-type ground substance
for shock absorption and protection
bone:
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calcified (made rigid by calcium salts, minerals)
for weight support
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Supporting CT #1: Cartilage
Cartilage Structure
Matrix:
z Proteoglycans derived from chondroitin sulfates
(polysaccharide) makes it gel-like
z Different cartilage types derive their properties from
the number and type of proteoglycans and the
number and type of protein fibers
Cells:
z chondrocytes, surrounded by lacunae (chambers)
z chondroblasts (progenitor of chondrocytes)
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No blood vessels:
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Perichondrium (a dense irregular CTP):
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chondrocytes produce antiangiogenesis factor
outer, fibrous layer (for strength)
inner, cellular layer (for growth and maintenance)
Cartilage Growth - Appositional
Cartilage Growth - Interstitial
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Interstitial growth (inside-out) by
chondrocytes
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Appositional growth (adding to the outside)
[Adults]
Figure 4–13a
The 3 Types of Cartilage
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Hyaline (glass) cartilage:
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Elastic cartilage:
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most common
translucent matrix, packed collagen
no prominent fibers
joint perichondrium
tightly packed elastic fibers
Fibrocartilage:
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very dense collagen fibers
joint pads
Figure 4–13b
Connective Tissue: Hyaline
Cartilage
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Amorphous, firm matrix with imperceptible
(clear) network of collagen fibers
Chondrocytes lie in lacunae
Supports, reinforces, cushions, and resists
compression
Forms the costal cartilage (ribs)
Found in embryonic skeleton, the ends of
long bones, nose, trachea, and larynx
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Connective Tissue: Hyaline
Cartilage
Hyaline Cartilage
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Reduces friction in joints
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Cover the end of long bones
Figure 4–14a
Figure 4.9f
Connective Tissue: Elastic
Cartilage
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Connective Tissue: Elastic
Cartilage
Similar to hyaline cartilage but with more
elastic fibers
Maintains shape and structure while allowing
flexibility
Supports external ear (pinna) and the
epiglottis
May be stacked up
Figure 4.9g
Connective Tissue:
Fibrocartilage
Elastic Cartilage
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Flexible support
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found in external ear and epiglottis
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Matrix similar to hyaline cartilage but less firm
with thick collagen fibers
Provides tensile strength and absorbs
compression shock
Found in intervertebral discs, the pubic
symphysis, and in discs of the knee joint
Figure 4–14b
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Connective Tissue:
Fibrocartilage
Fibrocartilage
Figure 4.9h
Connective Tissue: Bone
(Osseous Tissue)
Joints
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Most joints have both hyaline cartilage and
fibrocartilage in them
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Hard, calcified matrix with flexible collagen fibers
found in bone
Osteocytes are found in lacunae and are well
vascularized:
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Connective Tissue: Bone
arranged around central canals within matrix
small channels through matrix (canaliculi) access blood
supply (no diffusion through matrix)
Supports, protects, and provides levers for muscular
action
Stores calcium, minerals, and fat
Marrow inside bones is the site of hematopoiesis
Bone
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Very little ground substance
matrix is 2/3 Calcium salts (phosphate,
carbonate), 1/3 collagen
Figure 4.9i
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Bone: what to look for
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Osteon (whole circular structure)
Concentric lamellae (of matrix)
Central canal (at center of lamellae)
Osteoblasts
Osteocytes in lacunae
Canaliculi – canals for diffusion
Bone growth
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Close Up: ostocyte and
canaliculi
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Cytoplasmic extensions
Comparing Cartilage
and Bone
Appositional only (outside)
Osteocytes secrete matrix fibers and calcium
salts, forms concentric rings
Table 4–2
Nervous Tissue
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Nervous Tissue
Also called neural or nerve tissue:
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Branched neurons with long cellular processes
and support cells
specialized for conducting electrical impulses
rapidly senses internal or external environment
process information and controls responses
Found in the brain, spinal cord, and peripheral
nerves
Figure 4.10
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Muscle Tissue: Skeletal
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3 Types of Muscle Tissue
Long, cylindrical, multinucleate cells with
obvious striations
Initiates and controls voluntary movement
Found in skeletal muscles that attach to
bones or skin
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Skeletal muscle:
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Cardiac muscle:
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Smooth muscle:
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Muscle Tissue: Skeletal
large body muscles responsible for movement
found only in the heart
found in walls of hollow, contracting organs (blood
vessels; urinary bladder; respiratory, digestive
and reproductive tracts)
Muscle Tissue: Cardiac
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Branching, striated, uninucleate cells
interlocking at intercalated discs
Propels blood into the circulation
Found in the walls of the heart
Figure 4.11a
Muscle Tissue: Cardiac
Muscle Tissue: Smooth
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Sheets of spindle-shaped cells with central
nuclei that have no striations
Propels substances along internal
passageways (i.e., peristalsis)
Found in the walls of hollow organs
Figure 4.11b
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Muscle Tissue: Smooth
Developmental Aspects
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Primary germ layers: ectoderm, mesoderm,
and endoderm
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Three layers of cells formed early in embryonic
development
Specialize to form the four primary tissues
Nerve tissue arises from ectoderm
Figure 4.11c
Developmental Aspects
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Body Membranes
Muscle, connective tissue, endothelium, and
mesothelium arise from mesoderm
Most mucosae arise from endoderm
Epithelial tissues arise from all three germ
layers
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2.
3.
4.
are physical barriers that line or cover portions of
the body
Consist of an epithelium
Always supported by connective tissues
Mucous Membrane
4 Types of Membranes
1.
Membranes:
Mucous
Serous
Cutaneous
Synovial
Mucous membranes (mucosae):
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Epithelial surfaces must be moist:
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line passageways that have external connections:
digestive, respiratory, urinary, and reproductive
tracts
Goblet cells secrete mucins Æ mucus
to reduce friction
to facilitate absorption and excretion
Lamina propria:
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is areolar tissue
Figure 4–16
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Structure of Mucous
Membrane
Serous Membranes
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Line cavities not open to the outside; sealed
internal subdivisions of ventral body cavity,
e.g. peritoneum
Are thin and transparent but strong
Have fluid transudate to reduce friction
Epithelial part = Mesothelium (simple
squamous)
Connective tissue part = areolar tissue
Figure 4–16a
Serous Membranes
Structure of Serous Membrane
Figure 4–16b
Double Membranes
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Serous membranes:
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have a parietal (wall) portion covering the cavity
and a visceral portion (serosa) covering the
organs
Serous membranes:
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Figure 4.12c
Cutaneous Membrane
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Cutaneous membrane:
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is skin, surface of the body
thick, waterproof, and dry
Made up of epidermis and dermis (papillary and
reticular layers). What types of tissues?
consist of parietal layer and visceral layer
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Structure of
Cutaneous Membrane
Synovial Membranes
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Line articulating (moving) joint cavities
Produce synovial fluid (lubricant, nutrients to
chondrocytes of articular cartilage)
Protect the ends of bones (which themselves
are covered in what?)
Lack a true epithelium (incomplete, no basal
lamina)
Figure 4–16c
Structure of Synovial
Membranes
Summary: Inflammation
and Regeneration
Figure 4–16d
Aging
Figure 4–20
Proteoglycans
Epithelia get thinner
CT more fragile
SoÆ bruise easily, bones more brittle
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Different PGs made by chondrocytes
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Summary
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Connective tissues – structures and functions
CTP (loose, dense)
Fluid (blood, lymph)
Supporting (cartilage, bone)
Nervous tissue – brief overview
Muscle tissue overview (3 types)
Membranes (4 types)
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