Connective Tissue Flashcards
Lamina lucida
Has adhesion molecules: integrins and laminin
Lamina densa
Has type IV collagen and fibronectin
Basal lamina
Lamina lucida + lamina densa
Acts as a filtration system and attachment point
Made primarily by epithelial cells
Lamina reticularis
Made by fibroblasts
Type III collagen=reticular fibers
Type IV and VII collagen=anchoring proteins
Basement membrane
Lamina Reticularis + Basal Lamina
Tendons you can find
DRCT made of type I collagen
What makes collagen?
Fibroblasts
How to best ID fibroblasts in DRCT in tendon
Oval/flattened shaped nuclei in boxcar effect
Type of stain used for elastic membranes?
Weigert’s resorcin fuschsin stain
Most abundant cell in connective tissue
fibroblast
DICT primary components
fibroblasts and collagen type I
Loose connective tissue is able to
Support tissue and provide space in ECM for occupancy of cells and passage of fluid or transport tissues
Which CT contains fewer fibers and more interfiber space
Loose CT
Fibroblasts are derived from
mesoderm
Connective tissue is derived from
mesoderm
T/F The supporting role of the stroma is usually but not always fulfilled by CT
True
Functions of CT (5)
Structural support Medium for nutrient waste exchange Defense/Proection of body (physical & mediated actions) Energy storage Repair after injusry
Classification of CT (2)
Ordinary CT
Special CT
Types of special CT
adipose
blood
cartilage
bone
What is CT primarily made of?
ECM and cells
Categories of cells in CT
Fixed and transient cells
Components of ECM in CT
ECM=intercellular substance between and around cells
- Fibers
- Ground substance
Fibers in CT are
Formed elements that resist tensile forces
Ground substance in CT are
AKA amorphous material
Resist compressive forces
Types of fibers in ECM
Collagen fiber
Reticular fiber
Elastic fiber
Collagen fibers
A part of ECM
Most abundant protein in body
Most abundant formed element (fiber) n body
White gross color
Example of collagen fiber
Tendons
How to make collagen fibers
Transcription–>Translation
After translation, preprocollagen molecule is made that’s made of a polypeptide alpha chain with Gly, Pro, hydroxyproline, and hydroxylysine.
3 preprocollagen molecules will align with each other and assemble to form a tight helical structure called PROCOLLAGEN molecule
Procollagen looks like tightly wound rope with frayed ends. Each propetide allows procollagen molecule to be solube and prevents spontaneous aggregation into collagen fibers within the cell
When the procollagen is about to be secreted, the terminal protein is removed via PROCOLLAGEN PEPTIDASE. And yields TROPOCOLLAGEN
Tropocollagen polymerizes in ECM to form FIBRILS
FIBRILS polymerize to form COLLAGEN FIBERS
Overview of collagen synthesis
preprocollagen–> 3 preprocollagen–>procollagen–>tropocollagen–>fibrils–>collagen fiber
What removes terminal protein of procollagen
Procollagen peptidase
T/F Collagen fibers have great tensile strength
true
Hoe many types of collagen are there
28
Do collagen fibers have a long half life?
Yes-very stable
Type I collagen synthesizing cells
fibroblast, osteoblast, odontoblast, cementoblast
Type I collagen function
Resist tension
Type I collagen location in body
dermis, tendon, ligament, capsules of organs, bone, dentin, cementum
MOST COMMON
Type II collagen synthesizing cells
chonrdroblasts
Type II collagen function
resists pressure
Type II collagen location in body
Hyaline cartilage, elastic cartilage
Type III synethsizing cells
fibroblasts, reticular cell, smooth muscle cell, hepatocyte
Type III function
Forms structural framework of spleen, liver, LN, SM, and adipose tissue
Type III location in body
Lymphatic system, spleen, liver, cardiovascular system, lung, skin
Type IV synthesizing cell
Epithelial cell, muscle cell, Schwann cell
Type IV functinon
Forms meshwork of lamina densa of basal lamina to provide support and filtration
Type IV location in body
basal lamina
Type VII synthezising cells
epidermal ells
Type VII function
Forms anchoring fibrils that fasten lamina densa to underlying laminsareticularis
Type VII location
Junction of epidermis and dermis
Type III collagen AKA
reticular fibers
T/F reticular fibers branch into delicate tiny networks
True
What prevents reticular fibers from becoming large
glycoprotein coat
Oritenatin of reticular fibers allows what?
Abundant space allows bone marrow and lymph nodes and cells and fluids to go through
T/F reticular fibers are components of attachment
TRUE
See in basement membranes and external lamina
Reticular fibers are referred to as
Argyrophilic (silver)
A difference between elastic fibers and collagen
Elastic fibers can deform when stretched and return to original shape and can branch
Color of elastic fiber
Yellow-can see in nuchal ligament
Elastic fibers are made of
Elastin which is rich in Gly, Lys, Ala, Val, Pro, but NOT HYDROXYLYSINE
Explain orientation of elastin chains
They’re held together by four Lys molecules of diff elastin chains form covalent bonds with each other and form desmosine crosslinks.
Dsmosine crosslinks
Found in elastic fibers. Are highly deformable and impart high degree of elasticity.
Elasin molecules are surrounded by
Microfibrils which are made of glycoprotein=fibrillin. Myofibirls help form elastic fibers
Formation of elastic fibers
Fibroblasts and smooth muscle cells secrete molecular subunits to make fibrillin microfibrils.
Elastin is deposited on scaffold of microfibrils and amorphous growing structure forms
Elastin accumulates and occupies most of the electron dense center of the single elastic fiber. Fibrillin microfibrils remain at fiber surface.
T/F elastin resists digestion by most proteases
T
What is elastin hydrolyzed by
Pancreatic elastase
Unlike collagen, elastin can form
“sheet” AKA elastic membrane or elastic lamina
Elastic membranes are prominent where
Arteries
Elastic membranes can be formed by?
CT cells (fibroblasts) and smooth mucles cells
What is ground substance made of
complex sugars: GAGs, proteoglycans, multiadhesive glycoproteins
Purpose of ground substance
Fills space between cells and fibers in CT and serves as lubricant and barrier to penetration of invaders
GAGs
- Long chains of repeating disaccharides (unbranched and (-) charge)
- Amino sugar is one repeating subunit. Sugars have (-) charge making it polar molecule and attracting water and forms HYDRATED GEL WHICH RESISTS COMPRESSION.
GAGs come close together, (-) repel them and reslts in slippery texture to resist compression
Act as diffusion barrier
What allows GAG to resist compression?
(-) charges
Proteoglycan orientation
Like a test tube brush
Core protein is handle that allows GAGs to attach covalently (the bristles) Adhesion moecules attach proteoglycan to something like hyaluranic acid.
Proteoglycan charge and function
Negative
Allows water attraction and repulsion of other preotglycans which forms hydrated gel and acts as diffusion barrier
Aggrecan found where
Proteoglycan macromoleucle in cartilage and CTP that contains GAGs and hyaluronic acid.
Purpose of aggrecan
Massive molecule responsible for gel state of ECM and acts as barrier to diffusion
How bacteria combat ECM
Secrete hyaluronidase which cleaves hyaluronic acid into fragments and gets ride of gel state of ECM. This allows for rapid spread of bacteria.
Glycoproteins makeup
Non-filamentous cell adhesion molecules that have binding sites for ECM components and integrin moleules of CM that facilitate attachment of cells to ECM
Glycoprotein purpose
Mediates interactions between cells
1-permanent=integrins (adhesion molecules), growth factors
2-Transient=Ilk, GF, tumor necrosis factors, interferons, hormones, plasma proteins, chemokines
Examples of glycoproteins
laminin and fibronectin
Laminin found
Basal lamina and external laminae
Fibronectin found
throughout ECM
Purpose of laminin and fibronectin
Help bind molecules to ECM and help with cell migration and maintaining tissue structure
Types of ordinary CT
DRCT/DICT
Loose CT
Reticular CT
DRCT made of and find in and good for
Collagen or elastic
Tendons, laigaments, cornea
Good for linear tensile strength
Primary producer of collagen
Fibroblast
DICT made of found in and good for
Collagen or elastic
Dermis, capsules of organs, periosteum
Can be pulled in all directions
Loose CT AKA found in
Areolar CT
Superficial fascia, lamina propria of intestine
Reticular CT found in/special ID
Internal frameowkr of spleen and LN, basement membranes
Has high affinity for silver
Ehlers Danlos type VI disorder
Faulty lysine hydroxylation–>increased skin elasticity, rupture of eyeball
Scurvy disorder
lack of vitamin C, a required cofactor for prolyl hydroxylase–>ulceration of gums hemmorhages
CT fixed cells (7)
fibroblast fibrocyte pericyte adipocyte Mast cells Macrophages Myofibrocytes
CT transient cells (7)
Plasma cells Neutrophil Eosinophil Lymphocyte Macrophage Basophils Monocytes
Fixed cell defintion
Resident population of cells that developed and remain in place within the CT where they perform their function
These cells are stable and long-lived
Fibroblast
fixed or transient
most numerous where
produces
Fixed
Most numerous in CT
Produces/maintains ECM (makes fibers and most components of ground substance)
Fibroblast
- nucleus
- shape
- cytoplasm
- open faced (euchromatin)
- Spindle/fusiform shaped
- Cytoplasm not normally apparent but is visible in healing wounds due to amplified synethesis of proteins for ECM
When can you see cytoplasm of fibroblast
In tendon where there’s basophilic streaming
Damaged tissue needing repair
Myofibroblasts
- modified
- found where
Modified fibroblasts that are similar to fibrob;asts and smooth muscle cells
Found in areaus undergoing wound healing
How do myofibroblast help? How is it similar to fibroblast and smooth muscle
Speed wound healing by contracting the edges of wounds
Like muscle=contract with actin/myosin complex
like fibroblast=capable of creating ECM (type 1 and 3 collagen)
How is myofibroblast diff from muscle
Lack external lamina (basal lamina)
Pericytes AKA fixed? found where what kind of cell cytoplasm
Rouget or mural cells
Fixed
In walls of capillaries and venules
is an immature mesenchymal cell
cytoplasm has actin and myosin
Multipotential of pericytes
Can differintiate into other types of cells (myofibroblasts, SM cell, endothelial cell)
Pericytes function
Help with blood-brain barrier stability and angiogensis
Helps with blood flow regulating in microvasculature
Diabetic retinopathy
Caused by damaging pericytes in retinal vessels
Alzheimer’s disease
See increased number of pericytes in brain
Tumor vasculature
If tumor is weak and disorganized its partially due to inability of it to recruit pericytes.
Where to find pericytes? How do they respond?
Line small vascular vessels and respond to stimulation by constricting
What are pericytes very sensitive to?
Ischemia. When they die they constrict and stay constricted
Adipocytes
fixed?
Purpose
types
Fixed
store fat
Unilocular adipocyte and multiclocular adipocyte
Unilocular adipocyte ID fxn prominent metabolism controlled by how are they held together
Single large fat drop;et
E storage
Prominent smooth ER
Lipid metabolism
Under influence:insulin, corticosteroids, growth hormone, noepinephrine
External lamina holds cells together
Unilocular adipocyte AKA
Make
Endocrine tissue
Make leptin, adiponectin, adipokines, estrogen
Multilocular adipocyte
AKA
ID
FXN
Brown fat cell
Multiple small fat cell droplets and lots of mito (see uncoupling of oxidative phosphorylation)
Heat production ( E released as heat) see in neonatal and hibernating animals
Mast cells
Fixed?
Found
Most prominent in
Yes
See in CT of organs associated with body orifices, skin, and serous membranes
Prominent in LCT and blood vessels
Mast cells
mediate
Membrane receptor
Mediates anaphylactic shock (immediate hypersensitivity rxn)
IgE= stimulates degranulation
Primary mediators of Mast cells during degranulation (4)
Chondroitin sulfate
histamine
Eosinophil chemotactic factor (ECF)
Neutrophil chemotactic factor (NCF)
Secondary mediators of mast cells during degranulation (2)
prostaglandin
Leukotrienes
Same as histamine but 10x more powerful
ECF and NCF
Eosinophils limit magnitude of inflamm by mast cells by inactivating inflamm mediators like histamine and leukotrienes
Mastocytomas
Mast cell tumors
Mast cell tumors
Most common cutaneous tumors in trunks of :boxers, boston terriers, lab rets, beagles, schnauzers
Can effect HR, BP
Rx:surgery, chemo, antihistamines, tyrosinase kinase inhibitor
Leukocytes fixed include (5) Movement Origin
Transeient
PMN, Eosinophils, monocyte, lymphocyte, basophil
Circulate in peripheral blood and enter CT to perform special fxn
Bone marrow
Leukocytes are classfied as (2)
Granulocyte
Agranulocyte
Granulocytes
Contain
Lobes
Eosinophil
PMN
Basophil
Contain specific granules and primary granules
Lobed/segmented nucleus
Agranulocytes
Contain
Lymphocyte
Monocyte
Lack specific granules
Contain primary granules
Lymphocyte Granulocyte? Mediates ID Fxn Where
Agranulocyte
Mediators of specific types of immune response
Small cells with round nuclei and minimal cytoplasm
Scouts and weapons
Throughout msot CT but especially common in lamina propria (CT of mucous mem), splee, thymus, LN, peyer’s patches of ileum, tonsils.
MQ Granulocyte? Origin Abundant ID Fxn
Agranulocyte
Origin=monocytes. Once mono leaves blood it becomes MQ
Abundant lyosomes
variable morphology, “kidney bean” nucleus or oval eccentric open face nucleus
Phagocytosis, secretes cytokines, Ag presentation
Eosinophils
Granulocyte?
ID
Fxn
Yes
Granules stain intensely eosinophilic, Same size as neutrophils with band/elongated nucleus. Acidophilic cytoplasmic granules=lysosomes
Phagocytosis and destroys parasits (IgE) and limits inflammation initated by mast cells by neutralizing histamine and inhibiting mas cell degranulation via Eosinophil inhibitor factor
Neutrophil
Granulocyte?
ID
fxn
Yes
Most numerous leukocyte. Cytoplasmic granules are present (lysosomes) but don’t stain.
Acute phagocytosis of BACTERIA and creates pus. Also secretes inflam mediators and enzymes
Basophil
Granulocyte?
ID
Yes
Have large cytoplasmic granules that norm obscure 2 lobed nucleus. Stores histamine.
Plasma cell AKA Derived from Make Abundant
Plasma B cells, plasmocytes, effector B cells
From B lymphocytes
Make Ab
Abundant in RER
