Test 1 - Lecture 5 (connective) Flashcards
Where is connective tissue located?
underlies or surrounds muscle, nervous, and/or epithelial tissues
What items are found in the connective tissue?
cells & extracellular matrix (ECM)
What are 4 ways that connective tissue differs from epithelial tissue?
- cells not attached to each other
- cells are more randomly distributed
- space between cells is ECM
- embryonic origin is all 3 germ layers (epithelium is only mesoderm)
How is connective tissue classified?
by composition and organization of cellular and extracellular components and special functions
- types of cells present
- types of fiber present
- ground substance components
What is connective tissue proper?
How packed the fibers are and amount of ground substance
Describe the appearance of/what is found in loose connective tissue.
- thin, sparse collagen fibers
- lots of cells
- lots of ground substance
- viscous, gel-like
Where is loose connective tissue found?
- beneath epithelial mucosa and serosa
- associated epithelial glands
- around small blood vessels
Describe the appearance of/what is found in dense irregular connective tissue.
- mostly collagen fibers in bundles
- bundles in varying directions
- sparse cells
- little ground substance
Where is dense irregular connective tissue found?
- submucosa of hollow organs
- reticular layer of dermis
Describe the appearance of/what is found in dense regular connective tissue.
- sparse cells
- many collagen fibers
- fibers have organized parallel arrangement
- little ground substance
Where is dense regular connective tissue found?
- tendons
- ligaments
- aponeurosis
What features would help you distinguish between loose and dense irregular?
- amount of cells (loose has more)
- amount of fibers (dense irregular has more)
- ground substance (loose has more
Describe the appearance of collagen fibers with light microscopy vs. electron microscopy.
EM: highly striated tube-like structures
LM: eosinophilic w/ H&E (glycine and hydroxy p have positive charge)
How is collagen produced (short version-6)?
- mRNA formed in nucleus
- synthesis of pro-a chains on rER
- hydroxylation of proline & lysine
- glycosylation of specific hydroxylysl residues
- formation of procollagen triple helix
- helixes wrap to make full fiber
Type 1 collagen fiber
- loose and dense C.T.
- 90% collagen
- heterotrimeric
- gives resistance to force, tension, strength
- fibrillar
Type II collagen fiber
- hyaline and elastic cartilage
- resistance to pressure
- fibrillar
- homotrimeric
Type III collagen fiber
- loose C.T.
- makes reticular fibers
- fibrillar
- support scaffold for specialized cells
Type IV collagen fiber
- basal lamina
- support & filtration barrier
- not fibrillar
- sheet forming
Type VII collagen fiber
- anchoring fibrils of skin, eye, uterus, esophagus
- not fibrillar
- secure basal lamina to C.T.
Describe reticular fibers and why they do not stain well with H&E.
- type III
- 20 nm
- branching (tree)
it doesn’t stain well because all sugar groups in type III (no charge)
Describe elastic fibers and why they do not stain will with H&E.
- branching but thin like hair
- make a network with elastin and fibrillin
cannot be easily differentiated with collagen fibers in H&E
Consider the 3 fiber types (collagens, reticular, elastic). What are their functions and how does structure and function go together?
- collagen: tension & strength (big & “braided)
- reticular: support scaffolding & lymphatic system (branching network)
- elastic: keep from overstretching (thin, wiry, network)
How would you differentiate collagen and elastin fibers using electron microscopy?
collagen fibers are in individual fibers all clumped to make up one big one and elastin is all one big fiber with rough surface
What is ground substance and what is it made of?
It is the space between cells and fibers
- water
- proteoglycans
- multiadhesive glycoproteins
- glycosaminoglycans (GAGs)
Describe proteoglycans.
large molecules with protein core and many long chain polysaccharides (GAGs) covalently bonded to the core.
What are the different types of glucosaminoglycans?
In cartilage:
1. hyaluronic acid
2. heparin sulfate
3. chondroitin 4- & 6- sulfate
In other places:
4. heparin
5. dermatan sulfate
6. keratan sulfate
What are multiadhesive glycoproteins and what are their functions?
protein + small sugar group
- stabilized ECM & link to cell surface
- regulate functions of ECM to cell movement & migration
- stimulation of cell proliferation and differentiation
What are the multiadhesive glycoproteins?
- Fibronectin
- Laminin
- Tenascin
- Osteopontin
Fibronectin
cells attach to ECM (most abundant)
Laminin
attaches tissues together (basal lamina of BM)
Tenascin
embryonic (except injury/cancer)
Osteopontin
specific to bone - attaches osteoclast to bone spicule (bone reabsorption & remodeling)
What are the fixed cell populations in connective tissue?
- fibroblasts & myofibroblast
- mononuclear phagocytic system
- mast cells
- adult stem cells & pericytes
- adipocytes
What does a fibroblast do and are these a fixed cell population?
Yes.
1. make and secrete collagen, elastic, reticular fibers & complex carbs of ground substance
2. make majority of ECM & ground
3. activated in growth and wound repair
What are the functions of the MPS cells and are these a fixed cell population?
Yes
1. phagocytosis
2. secretion
3. antigen processing and presentation
What do mast cells do and are they a fixed population?
Yes
1. mediate hypersensitivity, reactions, allergies, and anaphylaxis
2. secrete histamines & leukotriene
Is adipose tissue solely for storage of lipids?
No, white provides insulation, cushioning for vital organs, and hormone secretion
Do brown adipocytes and white adipocytes arise in the same manner?
No, they have differing cell lineage, but both are from mesenchymal cells.
white - perivascular stem cells
brown - skeletal myogenic progenitor cell
- transdifferentiation
Where does one find white adipose tissue?
- subcutaneous C.T.
- greater omentum
- mesentery
- kidneys
- palms, soles
- orbit around eyeballs
What are some possible harmful effects of too much white adipose?
- increase eating (indirectly with leptin)
- increase inflammation
- increase blood pressure
Are white adipocytes true “cells”?
They have all the features of a “true cell” except for a plasma membrane… instead membrane similar to external lamina
What does it mean for brown adipose to be multi-ocular?
multi-ocular brown has multiple small sacs of lipids
uni-ocular white has one large sac of lipid
What is the function of brown adipose tissue?
heat production
Would you expect and adult human to have much brown adipose?
No, high in children/newborns (baby fat) and hibernating animals
