Connective Tissue Flashcards
Elements of connective tissues
Extracellular matrix
- ground substance
- protein fibers (collagen, elastic, reticular)
Resident cells
- mesenchymal
- macrophages
- adipocytes
- fibroblast
Connective tissue functions
- Matrix to support and physically connect tissues to form or
- Metabolic support
- Diffusion of nutrients and waste
- Defense
- Protect
- repair
What does connective tissue drive from?
Mesenchyme
Types of connective tissue
Proper: loose/dense and regular/irregular
Special properties: adipose, elastic, mucous, hematopoietic
Supporting: cartilage and bone
Loose connective tissue
Low collagen
High cells
High ground substance
Dense connective tissue
High collagen
Low cells
Low ground substance
What is the most abundant type of connective tissue
Loose connective tissue
- Most cell types present
Where is loose connective tissue located
Under epithelia
- forms storma (non essential)
Fills space between tissue and organs
Sheaths lymphatics and blood vessels
Dense regular vs dense irregular CT
Dense regular ct:
- collagen bundles are aligned in parallel
- tendons and ligaments
Dense irregular ct:
- collagen bundles are randomly arranged
- skin and stomach
dense regular CT locations
tendons and ligaments
Extracellular matrix composition
Fibers
Proteoglycans
Multi-adhesive glycoproteins
Three main types of fibers
Collagen fibers — collagen 1
Reticular fibers — collagen 3
Elastic fibers — elastin
What is the most abundant protein in the body?
Collagen
30% of dry weight
20+ types produced (mostly by fibroblasts)
General role of collagen
Resist tension and shear forces
Assembly of collagen
Peptide chains
Pro collagen
Tropocollagen
Collagen fibrils
Collagen fibers
Osteogenesis imperfecta
A genetic disorder that causes collagen formation to be incorrect or not enough (collagen I)
Collagen I fiber
Most abundant
Resist stretch
Provide tensile strength
Found in dermis, organ capsules, bone, tendons, fibrocartilage, scar tissue
Keloid scar
Excess collagen in wound healing
Collagen I fibers
Causes large scars
collagen types (locations/synthesis/function)
Reticular fibers
Collagen III
Smaller than type 1 collagen, no bundles
Provide structural framework and stability
Found in: Extensible organs (stretching)
Artery walls
Intestines
Uterus
Endocrine glands
Liver endometrium
Stroma of smooth muscle and hematopoietic organs
Collagen synthesis
Occurs in RER
proline hydroxylated to hydroxyproline
- requires Vitamin C
Collagenases or matrix metalloproteases (MMR) chew up collagen and remodel the ECM
Elastic fibers
ELASTIN core surrounded by fibrilin
Add resiliency to CT
Maintain extensible organs (expand)
Ground substance composition
Glycoconjugates (polysaccharides)
- glycosaminoglycans GAGs
- proteoglycans
- structural/adhesive glycoproteins
Tissue Fluid
Ground substance function
Store electrolytes and water
shock absorption
lubrication (form viscous barrier)
attachment and movement of cells in EMC
Glycosaminoglycans
GAGs
Keratin sulfate & heparin sulfate
Linear chain of repeating disaccharides
Negatively charged (hydrophilic)
Proteoglycans
GAGs + protein backbone
“Bottle brush”
Hydration
Viscous, resists compression
Proteoglycans aggregate
Aggrecan : Proteoglycans attached to a hyaluronic acid polymer
Holds water
Lubricates joints and organs
Structural/Adhesive Glycoproteins
Attach to ECM vie INTEGRIN receptors
- fibronectin & laminin
Permanent/resident cells
Fibroblasts
Macrophages
Mast cells
Adipocytes
Fibroblasts
Permanent/resident cell
Most abundant
Secret ground substance and fibers
Macrophages
Permanent/resident cells
Wound repair
Sensing damage (histocytes)
Phagocytosis
Secrete cytokines/enzymes
Phagocytic cell derived from monocytes and yolk sac progenitors
CT resident macrophages: histocytes
Mast cells
Permanent/resident cells
Inflammatory response
HISTAMINE/HEPRIN/LEUKOTRIENES
Found in dermis, respiratory tract, digestive tract
Long lived
Derived from precursor in bone marrow
Adipocytes
Permanent/resident cells
Whole body metabolism
Store lipids
Insulate
Make hormones
Single lipid droplet, flattened nucleus
Transient cells
Lymphocytes
Plasma cells
Neutrophils
Eosinophils
Lymphocytes
Transient cells
T lymphocytes: produce plasma cells
B lymphocytes: helper and cytotoxic cells
Few in CT
Plasma cells
Transient cells
Short-lived
“clock-face”
derived from B-lymphocytes
Produce ANTIBODIES
Neutrophils
Transient cells
Respond to tissue damage and infection
Lobed nucleus and granules
Eosinophils
Transient cells
Inflammatory/infection
Reddish orange granules
What cells release histamine?
Mast cells
anterior cruciate ligament
*parallel collagen fibers and few fibroblasts
A patient was seen in the ER after she fell while biking. The doctor determined that she had torn a structure in her lower leg. a biopsy of this structure shows numerous collagen bundles arranged in parallel and few visible cells. What structure is this?
-crural fascia
-peroneal tendon
-skin epidermis
-tibialis anterior muscle
-tibial nerve
peroneal tendon
dense regular connective tissue (tendons): arranged in parallel and few cells
An 8-year-old female presents in the ED with hives, itching, dizziness, and shortness of breath following an insect bite. What connective tissue cell is most likely responsible for her symptoms?
adipocytes
eosinophils
fibroblasts
macrophages
mast cells
mast cells
mast cells: resident cells of CT that contain many granules rich in histamine and heparin. inflammatory process. allergic reactions = mast cells
eosinophils= inflammation and asthma
macrophages/fibroblasts= secrete ECM
adiocytes= store energy
a 50-year-old woman presents with multiple oral blisters and a few blisters on her back. Blood tests reveal antibodies to a set of protein antigens and immunostaining of an oral mucosal biopsy shows the antigen throughout the epithelial layers. What structure is the defect?
a. aquaporin water channels
b. desmosomes
c. gap junctions
d. hemidesmosomes
e. tight junctions
b. desmosomes
which CT component is located in the ECM but not in the ground substance?
a. collagen bundles
b. fibronectin
c. glycosaminoglycans
d. hyaluronic acid
e. proteoglycans
a. collagen bundles
ECM = ground substance + fibers
*ground substance fills the space between fibers
ground substance = water, GAGs, proteoglycans, glycoproteins, fibronectin, laminin
What cell produces hormones that are important for metabolism and stores energy?
adipocytes
research scientists are attempting to create methods to prevent the movement (metastasis) of malignant tumors. a new drug is marked that triggers the apoptosis (cell death) pathway by disrupting a cell’s ability to adhere to the basement membrane. what is the target of this drug?
cadherins
demoplakin
fibrilin
integrins
occludens
integrins
integrins are receptors that help cell-to-cell and cell-to-ECM adhesion. the ligands that bind these integrins are fibronectin and laminin.
desmoplakin: desmosomes - cell-to-cell attachment
fibrillin: elastic fibers
occludens: tight junctions
a child is seen in the clinic for “fragile skin”. Skin breaks and blisters easily. Pt has a mutation in the gene coding for keratin 5, an intermediate filament that is expressed in basal cells of the epidermis. the oral cavity is NOT sensitive to stress. the reason for this difference is most likely that epithelial cells in the child’s oral cavity:
a. are ciliated
b. do not attach to a basal lamina
c. express different keratin genes
d. lack desmosomes
e. produce mucous
c. express different keratin gens
oral cavity epithelial do not express high levels of keratins
is skin and oral epithelia ciliated?
NO
which of the following cells produce the major protein component found in high abundance if scars?
a. adipocytes
b. fibroblasts
c. macrophages
d. mast cells
e. plasma cells
b. fibroblasts
fibroblasts produce Collagen I, found in scar tissue
what feature of epithelial cells contributes to their role in selective permeability and surface specialization?
polarity with distinct apical and basal surfaces
what best describes a unique characteristic of epithelial cells that aids in their protective function?
tight junctions between cells that create a continuous barrier
Individuals with Marfan’s syndrome have a genetic mutation that impairs fibrillin synthesis in CT, resulting in abnormalities of the ocular, musculoskeletal, and CV systems. Which cell type would this mutation lead to abnormalities?
fibroblasts
fibroblasts secrete fibrillin (ECM)
mast cells
MAST CELLS = ALLERGIC REACTIONS
