Download Connective Tissue (CT)

• There are 4 types of epithelial membranes:
1. Serous Membranes
• Line body cavities that
do not open to the
outside
• Reduce friction
• Inner lining of thorax
and abdomen
• Cover organs of thorax
Types of
and abdomen
• Secrete serous fluid
Membranes
2. Mucous Membranes
• Line tubes and organs
that open to outside
world
• Lining of mouth, nose,
throat, etc.
• Secrete mucus
3. Cutaneous Membranes
• Covers body
• Skin
4. Synovial Membranes
• Composed entirely of
connective tissue
• Lines joints
-Connective Tissue
-Muscle Tissue
-Nervous Tissue
 Most abundant tissue in body
 Composed of cells, fibers, and
extracellular matrices
 Cells usually divide
Connective
Tissue (CT)
 Varying degrees of vascularity
 Many Functions:
 Protection, defense and repair
 Insulation (fat storage)
 Produce blood cells
 Transportation
 Binding, support and packaging
 Fibroblasts
 Most common
 Star-shaped, fixed cell
 Secretes protein into matrix
producing fibers.
Connective
Tissue Cells
 Macrophages
 Wandering cells
 Act as scavengers (phagocytosis)
in injury/infection
 Mast Cells
 Fixed cells
 Release heparin (anticoagulant),
and histamine (promotes
inflammation).
Fibers (produced by fibroblasts)
 Collagenous
Connective
Tissue Fibers
(Collagenous
fibers)
 Thick pieces of protein (collagen).
 Inelastic.
 Hold structures together.
 High tensile strength.
 Ligaments, tendons.
 Lots of collagenous fibers =
Dense CT (white fibers)
 Few collagenous fibers = Loose CT
Elastic Fibers
Connective
Tissue
(Elastic
fibers)
Composed of bundles of
elastin (elastic protein).
Branching fibers
Not a lot of tensile
strength but very
flexible
Appear yellow in color.
Found in vocal cords, air
passages of respiratory
system.
Reticular Fibers
Connective
Tissue
(Reticular
fibers)
•Very thin collagenous
fibers that branch to form a
supporting network.
CT Matrix
CT cells not adjacent to each
other, but have intercellular
material (matrix) between them
 Matrix is made of cells and
consists of gel-like fluids and
protein fibers
CT
The general categories of
connective tissue are:
CT Proper
CT
 Loose CT
 Adipose tissue
 Reticular CT
 Dense CT
 Elastic CT
 Specialized CT
 Cartilage
 Bone
 Blood
Loose CT:
 Mainly fibroblasts
 Fluid to gel-like matrix
 Collagenous & elastic fibers
 Bind skin to structures
 Beneath most epithelia
 Blood vessels nourish it
 Between muscles
Collagenous
fiber
Fibroblast
Ground
substance
Elastic
fiber
(a)
(b)
Loose CT (Areolar Tissue)
• Not very well organized.
• It contains fibroblasts, matrix, some fibers scattered about.
• It functions to support underlying structures, and helps keep skin
bound to the body.
• Loose connective tissue is
found in the dermis and
subcutaneous layers of the
skin as well as surrounding
muscles.
• Sometimes it is called fascia.
 Adipose CT – made of cells (adipocytes) that contain
triglycerides.
 The lipid is used to store energy to be used by the body
 Adipose tissue is also found around some organs and joints
and forms a cushion for shock absorption.
 Adipose tissue also insulates the body.
 Beneath skin, behind eyeballs, around kidneys and heart
Cytsol
Fat droplet
Cell
membrane
Nucleus
(a)
(b)
Lipid
Nucleus of adipocyte
Here is a close up of adipose tissue. You can see the large-filled
adipocytes.
Adipocytes
Here’s another view of adipose tissue.
Reticular connective tissue consists of a thin
supportive network of reticular fibers.
It supports internal organ walls
 The walls of the liver, spleen, and lymphatic organs.
CT:
Reticular CT
Collagenous
fibers
White blood
cell
Fibroblast
(a)
(b)
Reticular connective tissue is web-like and forms a supportive
network.
 Dense (fibrous) CT contains thick collagenous fibers packed
together.
 It is found in ligaments and tendons (which have a high
tensile strength). Dermis of the skin.
 Binds body parts together
 Dense connective tissue has a poor blood supply
 It also contains some elastic fibers, few fibroblasts.
Fibroblasts
Collagenous
fibers
(a)
(b)
Dense regular
CT
Dense irregular
CT
• Fibers are parallel and
dark-staining
• Fibers are neither
parallel nor dark-staining
Elastic connective tissue contains many more elastic
fibers than collagenous fibers.
Contains fibroblasts
It is found in attachments between bones like the
vertebrae, and in the walls of some hollow internal
organs, heart, airways, large arteries.
Collagenous
fibers
Fibroblast
Elastic fibers
(a)
(b)
Elastic CT
Osseous tissue (bone) has a solid matrix
Functions to support, protect, form blood cells
Attachment point for muscles
Osteocytes (bone cells) are located in lacunae
Osteon
Lamella
Central
canal
Osteocyte
in lacuna
Canaliculi
(a)
(b)
Osteocyte
Nucleus
Cell process in
canaliculus
• Bone = most rigid CT; hardness comes from mineral salts such as calcium
phosphate and calcium carbonate.
• It is highly organized into units called osteons.
• The primary cell of bone is the osteocyte.
• Canaliculi are the canals between the lacunae (small spaces)
• Lamellae is the thin plate of bone matrix (rings)
 Cartilage is rigid and strong, so it
can provide support and
protection. It also forms a
structural model for developing
bones.
Specialized
CT:
Cartilage
 Cartilage consists of cells called
chondrocytes
 Cartilage has no direct blood
supply, so nutrients must enter by
diffusion.
• Hyaline cartilage
• Cartilage
• Rigid matrix
• Chondrocytes in lacunae
• Poor blood supply
• Three (3) types:
• Hyaline Cartilage
• Elastic Cartilage
• Fibrocartilage
• Most abundant
• Ends of bones
• Nose, respiratory passages
• Embryonic skeleton
• Elastic cartilage
• Flexible
• External ear, larynx
• Fibrocartilage
• Very tough
• Shock absorber
• Intervertebral discs
• Pads of knee and pelvic girdle
 Nutrients diffuse into cartilage
 The tissue needs water to help
move these substances in
Specialized
CT:
Cartilage
 As humans age cartilage tends to
“dry up” or become dehydrated
which lends to degeneration of
the tissue.
 The cartilage cells or
chondrocytes also do not divide
very frequently, which
contributes to poor healing.
Chondrocyte
Lacunae
• Hyaline cartilage has chondrocytes surrounded by lacunae, as shown above.
• It also has a glassy-appearing matrix.
• It is found at the ends of bones, the soft part of the nose, larynx and trachea.
• Hyaline cartilage serves as a model for bone growth.
Another picture of hyaline cartilage.
Elastic fibers
• Elastic cartilage also has the characteristic chondrocyte in lacuna appearance,
along with elastic fibers.
• This cartilage is found in the larynx and the ear.
• Fibrocartilage is characterized by rows of chondrocytes (in lacunae).
• It is a very strong cartilage, and is found in the intervertebral discs.
Hyaline cartilage
Nucleus
Lacuna
Chondrocyte
Extracellular
matrix
(a)
(b)
Elastic cartilage
Elastic fibers
Nucleus
Lacuna
Chondrocyte
Extracellular
matrix
(a)
(b)
Fibrocartilage
Lacuna
Chondrocyte
Nucleus
Collagenous
fiber
Extracellular
matrix
(a)
(b)
• Blood is also considered a connective tissue. It consists of cells suspended in a
matrix of fluid called plasma. (RBCs, WBCs, platelets)
• It transports gases such as oxygen and carbon dioxide, and functions in clotting and
immunity.
White blood
cell
Red blood
cells
Plasma
(extracellular
matrix of blood)
Platelets
(a)
(b)
Muscle Tissue
• Skeletal muscle
• General characteristics:
• Muscle cells also called
muscle fibers
• Contractile
• Three (3) types:
• Skeletal muscle
• Smooth muscle
• Cardiac muscle
• Attached to bones
• Striated
• Voluntary
• Smooth muscle
• Walls of organs
• Skin
• Walls of blood vessels
• Involuntary
• Non-striated
• Cardiac muscle
• Heart wall
• Involuntary
• Striated
• Intercalated discs
• Skeletal muscle is striated (caused by the density of overlapping protein
filaments called actin and myosin).
• Voluntary – we can control this
• It moves the muscles
• Located on muscles usually attached to bones
• Multinucleate – contain multiple nuclei per cell
• Cardiac muscle is also striated, but has a unique structure called an
intercalated disc.
• The disks are special intercellular junctions that allow
electrochemical impulses to be conveyed across the tissue.
• Found only in heart, and its main function is to allow the heart to beat.
• Involuntary – because we cannot control this
• Uninucleate – contain only one nucleus per cell
Skeletal Muscle
Striations
Nuclei
Portion of a
muscle fiber
(a)
Cardiac Muscle (b)
Striations
Nucleus
Intercalated
disc
(a)
(b)
Cytoplasm
Nucleus
(a)
(b)
• Smooth muscle is involuntary – we cannot control this
• It is non-striated because the myofilaments are not as dense as in cardiac
and skeletal muscle.
• Smooth muscle is found in organs such as in the gastrointestinal system and
the arteries.
• Smooth muscle function is to regulate all internal organs’ movements, like
stomach, liver, kidneys.
• Uninucleate – contain only one nucleus per cell
 Nervous tissue consists of nervous system cells called
neurons, and supportive cells called glia (they bind &
support nervous tissue).
 Nervous tissue function is sensory reception and conduction
of nerve impulses
Nervous
Tissue
Found in brain, spinal cord, peripheral nerves
Cellular
process
Cytoplasm
Nucleus
Cell
membrane
Neuroglial
cells
(a)
(b)
Neuron
Glial cell
• Nervous tissue contains neurons and glial cells.
• Neuron has a main cell body called a soma
• Neuron has dendrites that receive messages and a long axon
that sends messages