Histology: Connective tissue- Embryonic and Adult Connective Tissue 🔫 Flashcards
Where is connective tissue located?
It lies under the epithelia of all tissues and organs.
What does connective tissue do?
It provides both structural and metabolic support for the surrounding tissue.
What does connective tissue contain?
- rich network of blood vessels
- can contain adipocytes
What does the extra cellular matrix regulate?
- cell proliferation
- cell migration
- cell differentiation
What does epithelium tissue always have?
connective tissue beneath.
Why is epithelium tissue unable to get nutrition?
It does not have any blood vessels.
–> it cannot get nutrition, oxygen, it cannot undergo METABOLISM
What is the route of diffusion of nutrients and waste products?
nutrients: capillaries (connective tissue) –> epithelial tissue
waste products: epithelial tissue –> capillaries (connective tissue)
What are the principal functions of connective tissue?
1) provide support and form to the body and organs
2) aid in the defence and protection of the organism
3) serve as a medium of exchange of nutrients between tissues
4) store fat and thermoregulate
What is an example of connective tissue (support)?
- cartilage
- bones
What is an example of connective tissue (defense and protection)?
white blood cells, fight against pathogens, bacteria, paracytes, viruses etc.
What is an example of connective tissue (medium of exchange of nutrients)?
red blood cells (erythrocytes)
What is an example of connective tissue (fat and thermoregulation)?
loose and dense connective tissue ??
What is the role of adipose tissue? What is its non-prefessional name
adipose tissue=fat tissue
storage of energy
What is connective tissue composed of?
cells and an extracellular matrix (ECM) (fibers and ground tissue).
What is the “ECM”?
the ExtraCellular Matrix
What does the extracellular matrix consist of?
- PROTEIN FIBERS (collagen, elastic and reticular fibers)
- amorphorus component containing specialized molecules (proteoglycans, multiadhesive glycoproteins, and glycosaminoglycans) that constitute to the GROUND SUBSTANCE.
What are the three principal types of connective tissue fibers?
1) collagen fibers
2) reticular fibers
3) elastic fibers
What are collagen fibers?
- flexible
- high tensile strength
- formed from collagen fibrils
- formation: fibroblasts and ECM
- most abundant type of fibers
What are collagen fibers formed from?
collagen fibrils
What does collagen fiber formation involve?
events that occur:
1) within the fibroblasts- production of procollagen molecules
2) outside the ECM- polymerization of collagen molecules into fibril, which are assembled into larger collagen fibers.
Where does the production of procollagen molecules occur?
fibroblasts
Where does the polymerization of collagen molecules into fibril occur?
outside the extracellular matrix.
What type of fibers is most abundant in connective tissue?
collagen fibers
What type of fibers are most flexible?
elastic fibers
How are elastic fibers produced?
Elastic fibers are produced by fibroblasts and smooth muscle cells.
What do elastic fibers allow epithelial tissues to do?
respond to stretch and distension.
distention- act of swelling
What are elastic fibers composed of?
a CENTRAL CORE OF ELASTIN associated with a network of FIBRILLIN MICROFIBRILS (made up of fibrillin and emilin)
What are fibrillin microfibers composed of?
fibrillin and emilin
Q. What type of fibers does a human ear contain?
a lot of elastic fibers, and a few collagen fibers
(it returns to its shape when moved)
What is the major difference between collagen and elastic fibers?
Collagen fibers:
- THICKER
Elastic fibers:
- THINNER
What are the major fibers found in the skin? The ear?
skin:
collagen fibers>elastic fibers
ear:
elastic fibers>collagen fibers
What is the name of the rarest type of fibers?
Reticular fibers
What are reticular fibers composed of?
type III collagen
What is the primary function of reticular fibers?
- provide a supporting framework for cells in various tissues and organs
THEY ARE VERY SPECIALIZED!!
Where are reticular fibers abundant?
in lymphatic tissues
Where are reticular fibers produced? By what cells?
in the LYMPHATIC and HEMOPOIETIC TISSUES, reticular fibers are produced by specialized RETICULAR CELLS.
in most OTHER TISSUES, reticular fibers are produced by FIBROBLASTS.
Where can reticular fibers be found?
found mostly in IMMUNE SYSTEM ORGANS:
- lymph node
- bone marrow
What do reticular fibers + other cells form?
An environment allowing for immune system cells to develop.
(chemical environment)
What happens when the organism has problems with reticular fibers and tissues?
the immune system isnt able to fully develop –> no good immune response –> no/weak protection from pathogens, viruses, bacteria etc.
What is the ground substance?
A part of the extracellular matrix.
What is the ground substance composed of?
- proteoglycans
- hydrated glycosaminoglycans (GAGs)
- multiadhesive glycoproteins
What is a ‘proteoglycan aggregate’?
Proteoglycans indirectly bind to hyalunoran (by special link proteins) to form a giant molecule called the proteoglycan aggregate.
What does the binding of water to a proteoglycan aggregate do?
It regulates the movement and migration of macromolecules, microorganisms or metastatic cancer cells in the ECM.
What type of structure does the ground substance have?
non-cellular structure
similar to a gel: mostly water but also contains chemical substances
What is the primary purpose of proteoglycans and glycosaminoglycans?
strengthen joints and cartilage
What are the two types of connective tissue cells?
1) resident cell population
2) wandering (transcient) cell population
What is the resident cell population? State examples.
- relatively stable and nonmigratory connective tissue cell population
include:
- fibroblasts
- myofibroblasts
- macrophages
- adipocytes
- mast cells
- adult stem cells
What is the wandering cell population? What is its different name? State examples.
Wandering stem cells = Transcient stem cells
- primary cells that have migrated from blood vessels
include all immune system cells:
- lymphocytes
- plasma cells
- neutrophills
- eosinphils
- basophils
- monocytes
What type of connective tissue cells are responsible for an immune response?
wandering (transcient) cells
What is the principal cell type
of connective tissue?
fibroblasts
What are fibroblasts responsible for?
synthesis of collagen and other components of the ECM.
What are macrophages?
Phagocytic cells that contain an abundant number of lysosomes and play an important role in immune response reactions.
Phagocytes phagocytize organic and non organic molecules. Begins an immune response as ot acts as an antyigen presenting cell.
What are adipocytes?
Specialized connective tissue cells that store neutral fat and produce a variety of hormones.
What are mast cells? What do they contain?
- develop in bone marrow and differentiate in connective tissue
- contain basophylic granules that store mediators of inflamation
What are adult stem cells? Where are they located?
- reside in specific locations (called niches) in various tissues and organs
- difficult to distinguish from other cells of connective tissues
What is a “niche”?
The place in which stem cells are located.
What is the relevance of fibroblasts? How are they created?
Without fibroblasts there are no fibers or ground substance.
Without fibroblasts there would be no tissue at all.
Created from stem cells.
What are the two classifications of connective tissue?
1) EMBRYONIC connectove tissue
2) ADULT connective tissue
ADULT: connective tissue proper and specialixzed connective tissue
How does adult connective tissue further subdivide?
2.1 connective tissue proper (universal)
2.2 specialized connective tissue
Where is the embryonic connective tissue found?
in the embryo and fetus (before given birth)
What are the principal properties of connective tissues?
- considerable plasticity (allowing for changing of connective tissue types, ie. development of bone from cartilage/ligaments)
- regenerative capabilities due to undifferentiated cells. (high- loose bone tissue, limited- mature cartilage)
What are the principal properties of the extracellular matrix?
- medium of transport
- structural function (molecules resistant to tension, compression, and hard inorganic crystals)
- allows for mutual shifts, and mutual mobility
What is the name of tumours originating from connective tissue cells?
sarcoma
What is “connective tissue proper”?
The group of soft connective tissue.
What is the dominant parts of connective tissue proper loose?
1) connective tissue cells
2) ground substance: extracellular matrix
(good blood supply, innerviation and presence of immune cells)
What are the features of loose connective tissue?
1) mobility
2) changes of shape
3) fills gaps between organ layers
4) contains adipose cells (important in metabolism and hormone production)
What two tissues are considered loose embryonic connective tissue?
1) mesenchyme
2) jelly-like umbillical chord tissue
What are the dominant parts of connective tissue proper dense?
extracellular matrix fibers
What do all cartilage types share?
- a composite structure of am extracellular matrix
- fibrous part connected to cartilage cells occuring individually or in groups.
- fibers are also connected to high-molecular protein-polysaccaride complexes of the ground substance.
What is the most common cartilage type?
hyaline cartilage
What are the connective tissue types?
1) connective tissue proper
2) cartilage
3) bone
What are wandering cells?
Cells which migrate into the connective tissue from the circulatory system.
What are resident cells?
Cells which originate directly from the local area.
