Histology of connective tissue Flashcards
what does all connective tissues originate from
embryonic mesenchyme
developing mainly from mesoderm
What does connective tissues provide
Support
Binds tissues together
Protects tissues and organs of the body
3 main components of connective tissues
Cells
Protein fibres
Amorphous ground substance
What makes up amorphous ground substance
Proteoglycans
Glycoaminoglycans
Glycoproteins
What do the fibers and ground substance make up
Extracellular matrix
Classifications of connective tissues
Dense
Loose
Specialised
Dense
Regular and irregular
Loose
Areolar
Adipose
Reticular
Specialised
Blood
Lymph
Bone
Cartilage
Functions of connective tissues
Provides substance and form to the body and organs
Defends against infections
Injury repair
Cushion between tissues and organs
Stores lipids
Medium for diffusion
Attaches muscle to bone and bone to bone
Support
Loose areolar tissue
Forms layer beneath epithelial lining of many organs
Fills spaces between givers of muscle and nerve to provide support
Highly cellular with random collagen arrangement (some elastic and reticular)
Most numerous cells are fibroblasts
Numerous cells in loose connective tissues
Fibroblasts
Dense connective tissue overview
More collagen fibers with little ground substance and fewer cells (mainly fibroblasts)
Greater resistance to stretching
Poorly vascularised
Dense regular connective tissues
Mainly type 1 collagen fibers oriented in parallel direction
In tendons and ligaments
Dense irregular connective tissues
Collagen fibers woven in multiple directions
Resist tensile forces
Found in dermis
Types of fibers
Collagen
Elastic
Reticular
Collagen fibers
Most type one collagen, most abundant protein in body
Provide tensile strength, resistance to stretching
Elastic fibers
Contain elastin and fibrillin
Provide elasticity
Can be stretched but return to original length
Reticular fibers
Contain type 3 collagen
Provides support
Network of thin fibers
Type 1
Fibrils aggregate into fibers and fiber bundles
Most widespread
Forms component of extra cellular matrix/interstitial collagen, tendons, ligaments, capsules of organs
Type 2,
Fibrils don’t form fibers
Present in hyaline and elastic cartilages
Type 3
Fibrils aggregate into fibers
Present surrounding smooth muscle cells and nerve fibers
Forms strong of lymphatic tissues and organs
Type 4
Chemically unique form of collagen
Doesn’t form fibrils
Major component of basal lamina
what is in the image
elastic fibers
contain protein elastin along with lesser amounts of proteins and glycoproteins
after being stretched or compressed will return to original shape
first is in mesentery, dermis and then wall of aorta
what are elastic fibres composed of
elastin and fibrillin
which stain can view elastic fibres
H&E
what is in the image
reticular fibers
seen in lymph nodes
black fine lines
lymphoid cells stained red
which stain is used in reticular infers
by a silver impregnation method
argyrophilic
where are reticular fibres mainly located
in reticular tissue of soft organs such as liver and spleen
anchor and provide structural support to parenchyma
2 types of cells
fixed and transient
fixed cells overview
remain mostly stationary within connective tissue
perform functions where they are formed
fibroblasts, adipose cells
transient cells
free
originate mainly in the bone marrow and circulate in the bloodstream
leave to enter the connective tissue spaces to perform their specific functions
white blood cells: neutrophils, eosinophils, basophils, lymphocytes and monocytes
examples of fixed cells
chondrocytes
adipocyte
fibroblast
mesothelial cells
endothelial cells
osteocyte
examples of transient cells
t lymphocyte
plasma cells
osteoclast
macrophages
megakaryocyte
mast cell
neutrophil
eosinophil
basophil
b lymphocyte
what is in the image
fibroblasts
what is the most abundant type of cell in the connective tissue
fibroblasts
secrete ECM comp: collagen/elastin
types of fibroblasts
active
inactive
active fibroblasts
often reside close to type 1 collagen bundles
lie parallel to long axis of the fibers
elongated, fusiform cells possessing platelet staining cytoplasm
difficult to distinguish from collagen when stained with H&E
has a large darker stained granular ovoid nucleus with well defined nucleolus
inactive fibroblast
fibrocytes
smaller
more ovoid
nuclei are smaller and elongated
more deeply stained
do not manufacture ECM
what is in the image
loose connectie tissue
what is in the image
loose connective tissue
displays collagen and elastic fibre
under light microscope
what is in the image
dense regular connective tissue
sparse cytoplasm of fibroblasts not visible as blends with collagen fibres
is an image of a tendon
nuclei of fibroblasts appear as dark dots in rows between fibres
what is in the image
regular dense connective tissue
what is in the image
irregular dense connective tissue
general organisation of loose connective tissue
much ground substance
many cells
little collagen
randomly distributed
major functions of loose connective tissue
supports microvasculature
nerves
immune defence cells
examples of loose connective tissues
lamina propria
general organisation of dense irregular connective tissue
little ground substance
few cells
much collagen in random fibres
major functions of dense irregular connective tissue
protects and supports organs
resists tearing
examples of dense irregular connective tissue
dermis of skin
organ capsules
submucosa
general organisation of dense regular connective tissue
almost completely filled with parallel bundles of collagen
few fibroblasts
aligned with collagen
major functions of dense regular connective tissue
stron connections within musculoskeletal system
strong resistance to force
examples of dense regular connective tissue
ligaments
tendons
aponeuroses
corneal stroma
2 types of adipose tissue
white
brown
what is in the image
unilocular
develops from embryonic mesenchyme with formation of lipoblasts containing small fat vacuoles
mature to adipocytes, storing fat
lipid-storing support cells
act as physical cushioning and padding
arborizing capillary vessels transfer metabolites to and from cells
what is in the image
brown adipose tissue
multilocular
most prominent in newborn
develops as cluster of eosinophilic cells
abundant mitochondria for heat generation
has lipid rich cells with central nucleus and polyhedral shaped cells with granular pink cytoplasm
capillary vascular supply with thin fibrocollagenous septa divides tissue into small lobules
non shivering thermogenesis
increase in metabolic heat production (above the basal metabolism)
not associated with muscle activity
2 types of connective tissue membranes
mucous membranes
serous membranes
mucous membranes
line passageways into body that are continuous with exterior
digestive, urinary, reproductive and respiratory tracts
serous membranes
thin and transparent
line compartments of ventral body cavity
examples of serous membranes
pleura
peritoneum
pericardium
pleura
lining on lungs
pleural cavities in which lungs are found
peritoneum
lining of abdominopelvic cavity and all organs situated here
pericardium
lining on surface of heart and pericardial sac that surrounds heart
what do serous membranes consist of
simple squamous epithelium called mesothelium
thin underlying layer of areolar connective tissue
Ehlers-danlos syndrome
abnormal skin laxity
hyper mobility of joints
predisposes to recurrent joint dislocations
lots of genetic subtypes
disease can be caused by mutation in collagen gene or in enzyme related to collagen metabolism
marfan syndrome
mutation in fibrillar gene or dysfunction in its expression
elastic fibers can’t form without fibrillar
often have hyper mobile joints, heart valve dysfunction
patients often very tall and thin
features of cartilage
avascular, no nerve supply and no lymphatic drainage
surrounded by perichondrium except articular cartilage and fibrocartilage
has cell and extracellular matrix
cells of cartilage are chondrogenic cells, chondroblasts and chondrocytes
has tensile strength, firm structural support for soft tissues, allows flexibility without distortion, resilient to compression
shock absorber
how does cartilage grow
appositional and interstitial growth
difference between chondroblasts and chondrocytes
chondroblasts are immature cells that will develop into chondrocytes
3 types of cartilage
hyaline
elastic
fibrous
hyaline cartilage
perichondrium
most abundant and contains type 2 collagen fibers
degenerates when chondrocytes hypertrophy and die and matrix begins to calcify, part of endochondral bone formation
cells enclosed in lacunae
perichondrium
provides protection
nutrition
repair
what is in the image
hyaline cartilage
where is perichondrium not present
in articular surfaces
elastic cartilage
matrix that contains elastic and collagen, can recon when deformed
perichondrium rich in elastic fibers
has abundant fine to coarse branching elastic fibers interspersed with type 2 collagen fibre bundles
what is in the image
elastic cartilage
fibrocartilage
chondrocytes arranged in parallel rows
no perichondrium
resistance to mechanical forces
fibrocartilage possesses dense coarse type 1 collagen fibers in its matrix, aids it in withstanding tensile forces
what is in the image
fibrocartilage
where is hyaline cartilage located
temporary skeleton of the embryo
articular cartilage
cartilage of respiratory tract
costal cartilage
where is elastic cartilage located
external ear
epiglottis
auditory tube
where is fibrous cartilage located
intervertebral discs
articular discs of the knee
mandible
stenroclavicular joints
pubic symphysis
what is in the image
hyaline cartilage
what is in the image
elastic cartilage
what is in the image
fibrocartilage
what is in the image
hyaline cartilage of an articular surface of bone from synovial joint
what is in the image
elastic cartilage and perichondrium from th epiglottis
size of chondrocytes and lacunae will vary
elastic fibres are dark strands in extracellular matrix
orcein stain
what is in the image
hyaline cartilage and then intervertebral disc
chondrocytes appear oriented along lines of stress on cartilage and intervening layers of type 1 collagen
also has fibrocartilage at the top
identifying characteristics of hyaline cartilage
type 2 collagen
basophilic matrix
chondrocytes normally arranged in groups
perichondrium in most places except articular cartilages and epiphyses
identifying characteristics of elastic cartilage
type 2 collagen
elastic fibers
identifying characteristics of fibrous cartilage
type 1 collagen
acidophilic matrix
chondrocytes arranged in parallel rows between bundles of collagen
always associated with dense regular collagenous connective tissue or hyaline
two types of cartilage growth
interstitial
appositional
interstitial cartilage growth
individual mesenchymal ells retract processes and congregate in cell clusters to form chondrification centres
kartogenin will influence cells in the chondrification centres and differentiate into chondroblasts
secrete cartilage matrix and entrap in lacunae
when surrounded in matrix they are chondrocytes
chondrocytes divide by mitosis
which type of cartilage growth is shown in the image
interstitial
appositional cartilage groth
outermost cells are spindle shaped and clustered in perichondrium
inner cells, chondrogenic layer will differentiate into chondroblasts which synthesise and secrete type 2 collagen
which type of cartilage growth is shown in the image
appositional cartilage growth
bone overview
highly vascular
consists of cells, fibres and extracellular material with mineral deposits
important for haemopoiesis acts as reservoir for calcium and minerals
covered by periosteum except at articular surfaces
protects organs
primary and secondary
primary bone overview
abundant osteocytes
irregular bundles of collagen
later replaced by secondary bones
secondary bone overiew
categorised into compact and spongy
compact= cortical
spongy= cancellous/trabecular
label top to bottom
outer circumferential lamellae
interstitial system
inner circumferential lamellae
volkmann canal
Haversian canal\lacuna
endosteum
periosteum
medullary trabecular bone
where are osteocytes located
in spaces called lacunae
outer circumferential layer
form the outermost region of the diaphysis
sharpie fibers ancoring periosteum to the bon
trabecular of spongy bone
extend from inner circumferential lamellae into marrow cavity
interrupt endosteal lining of inner circumferential lamellae
label top to bottom
femoral neck
epiphysis
metaphysis
diaphysis
metaphysis
epiphysis
bone bit is periosteum
osteon
consists of central canal called osteonic/Haversian canal
surrounded by concentric rings of matrix
between rings of matrix
osteocytes
located in spaces called lacunae
periosteum
outer fibrous layer and inner cellular layer
what is in the image
osteon
compact bone
transverse section of osteon showing Haversian canal
canaliculi are very fine dark strands radiating from Haversian canal to osteocytes
only nuclei of osteocytes are clearly seen
canaliculi
spaces occupied by cytoplasmic processed of osteocytes
what is in the image
osteon
compact bone
shows Haversian canals
nuclei of osteocytes appear as small dark dots
some lie in concentric circles formed by lamellae of bone
black line surrounds some irregularly placed lamellae
what is in the image
compact bone
longitudinal section of osteons
nucleic are small dark dots
information about Haversian canals
lined by layer of osteoblasts and osteoprogenitor cells
houses neuromuscular bundle with associated connective tissue
volkmann canals
haverisan canals of adjacent osteons connected by these
vascular spaces that are oriented oblique or perpendicular to Haversian canals
identify the labels
Periosteum (FP)
Outer circumferential lamellae (OCL)
Interstitial lamellae (IL)
Haversian canal (HC)
Volkmann canals (VC)
Inner circumferential lamellae (ICL)
different types of bone cells
osteoprogenitor cells
osteoblasts
osteocytes
osteoclasts
osteoprogenitor cells
precursors of osteoblasts
osteocytes
derived from osteoblasts trapped within the bone they have made
regulate bone remodelling by secretion of several factors that act on other cell types
osteoblasts
synthesise osteoid collagen
mineralise if by depositing calcium and phosphate hydroxides
only large metabolically active cells when there is a requirement for new osteoid deposition
when inactive they are insignificant spindle cells lying on the bone surface
osteoclasts
multinucleate cells derived from blood monocytes
highly mobile cells capable of eroding mineralised bone by enzymic hydrolysis of osteoid collagen with release of bone minerals
osteoclastic resorption of bone stimulated by parathyroid hormone in response to low serum calcium level
important components of osteoid
type 1 collagen
protein osetocalcin
which binds Ca2+ and PO4 to form hydroxyapatite crystals
types of bone development
intramembranous
endochondral
bone develop in utero
as a hyaline cartilage model
becomes bone by endochondral ossification
some directly by intramembranous ossification
cartilage replaced as chondrocytes die and osteogenic cells become osteoblasts which deposit bone matrix on old cartilage matrix
intramembranous ossification process
- Mesenchymal stem cells aggregate and differentiate to form osteoblasts
- Form ossification centre
- Osteoblasts secrete osteoid (unmineralized bone
- Peripheral mesenchymal continue to differentiate
- Osteolasts secrete osteoid inwards towards ossification centre
- Osteoblasts become trapped in osteoid and are differentiated into osteocytes
- After several days the osteoid calcifes and hardens to form hardened bone matrix
- Osteoid continues to be deposited and assembles in random manner around embryonic blood vessels
- Forms finely woven trabeculae
- Mesenchyme begins to differentiate into periosteum
- Compact bone replaces woven bone at outer edge, layered structure
- Internal spongy bone remains as this is where vascular tissue in the spaces forms red marrow
- Osteoblasts remain on bone surface to remodel when needed
endochondral ossification process
- Starts at primary ossification centre
- Perichondrium becomes vascularised
- Blood vessels supply nutrients to mesenchymal cells
- Causes differentiation of mesenchymal cells to osteoblasts
- Osteoblasts will gather on diaphysis wall and form bone collar by depositing osteoid
- Bone colloar formation causes chondrocytes in the central cavity to enlarge and matrix to calcify
- Calcified matrix becomes impermeable to nutrients, causes cell death
- Central clearing forms where the cells have died
- Healthy chondrocytes at distal ends cause elongation as more cartilage deposited
- Periosteal bud invades cavity and forms spongy bone: contains arteries, veins, lymphatics, nerves, osteogenic cells (osteoblasts and clasts)
- Osteoclasts degrade cartilage matrix whilst osteoblasts deposit new spongy bone
- Bone continues to elongate distally
- Primary ossification centre continues to enlarge
- Osteoclasts now break down newly formed spongy bone from centre
- Forming the medullary cavity, early stages
- Cartilaginous growth now only occurs within the epiphyses
- Bony epiphyseal surface begins to form at both ends
- Secondary ossification may appear at one or both epiphysis (doesn’t develop yet)
- Epiphyses ossify after birth, 2 centres in long bones, 1 in short and several in irregular
- Cartilage now remains on bone surface and epiphyseal plates
- Articular cartilage on the ends
- Cartilage in the epiphysis
postnatal development of bone
epiphyseal plate remains across junction between epiphysis and diaphysis
1. Chondrocytes on epiphyseal side relatively inactive= resting zone
2. Chondrocytes undergo rapid mitosis and stack, pushes diaphysis away from epiphysis, cartilaginous matrix= proliferation zone
3. Older chondrocytes enlarge as lacunae erode ,cartilaginous matrix will harden = hypertrophic zone
4. Calcification zone= calcified matrix invades diaphysis
5. New empty space allows osteoblasts to deposit bone as osteoclasts erode the cartilage= ossification zone
when do the two ossification centres merge
when the epiphyseal plate disappears
primary centre of ossification
resting zone
zone of proliferating
zone of maturation hypertrophy and calcification
zone of degeneration
zone of ossification
zone of resorption
label the image
resting zone
normal hyaline cartilage
zone of proliferation
where isogenous groups of chondrocytes actively divide, forming linear isogenous groups. This zone maintains cartilage thickness.
zone of maturation, hypertrophy and calcification
where chondrocytes mature, hypertrophy and produce alkaline phosphatase with the subsequent calcification of the cartilage matrix.
zone of degeneration
where chondrocytes die, leaving empty lacunae surrounded by vertically oriented spicules of calcified cartilage
zone of ossification
where bone is deposited on the calcified cartilage spicules immediately adjacent to the bony diaphysis, thus increasing the length of that diaphysis.
zone of resorption
where calcified cartilage–bone spicules are resorbed to form the marrow space
secondary centre of ossification
occurs in each epiphysis
similar pattern to primary except:
1. No periosteal band is formed.
2. Ossification occurs in a radial manner from the original center of the secondary center of ossification.
3. Bone resorption does not occur; thus, spongy bone permanently fills the epiphyses.
4. Ossification does not replace articular cartilage.
what type of ossification is in the image
intramembranous officiation
which type of ossification is in the image
endochondral ossification
which type of ossification is in the image
postnatal development of bone
osteoporosis
age related
loss of bone mitral density
increased activity of osteoclasts after menopause as oestrogen levels decrease due to loss of secretion of hormones from ovaries
could be due to decreased level of calcium in bones
affected bones often fractures with minimal force
oestrogen therapy and high intake of calcium helps to slow disease progression
administration of calcitonin also inhibits bone resorption and can prevent post menopausal bone los
osteoarthritis
most common form
primarily disease of artilcualr cartilage
loss of cartilage leads to bone on bone contact in synovial joints with rapid deterioration of movement and function
disorder associated with decreased glycosaminoglycan content of matrix accompanied by increased water content
affects hyaline cartilage covering ends of articulating bones
particularly affecting weight bearing joints
endochondral ossification information
vast majority of bones
except the clavicle it will form all bones under the skull
begins in month 2 of in utero
uses hyaline cartialge for ossification
intramembranous ossification information
first present after conception
beofre week 8
all bone formed from hyaline cartilage and fibrous membranes
forms cranial bones and clavicle
