Histology: Connective Tissue- Adult Connective Tissue Flashcards
What are the two types of connective tissue proper?
1) Loose connective tissue
2) Dense connective tissue
What is a different name for loose connective tissue?
areolar connective tissue
How is dense connective tissue further subcategorised?
based on the organisation of its collagen fibers:
1) dense IRREGULAR connective tissue
2) dense REGULAR connective tissue
What is the structure of loose connective tissue?
- a cellular connective tissue with thin and relatively sparse collagen fibers,elastic and reticular fibers.
- the ground substance is abundant and occupies more volume than the fibers do
- viscous gel-like consistency
What is the primary purpose of loose connective tissue?
- diffusion of oxygen and nutrients from the small vessels that course through the connective tissue
- diffusion of carbon dioxide and metabolic wastes back into the vessels
Why is loose connective tissue called “loose”?
It contains very little fibers and components. Fibers do not overlap, it is easy to simply count them.
What is the most common component of loose connective tissue?
ground substance
What is the consistency of loose connective tissue?
- between solid and liquid
- gel like substance
Where is loose connective tissue located?
- beneath the epithelia that covers the body surfaces (eg. muscles),
- beneath the epithelia which lines the internal surfaces of the body,
- also associated with the epithelium glands,
- surrounds the smallest blood vessels.
What is loose connective tissue the initial site of?
Initial site where pathogenic agents such as bacteria that have breached an epithelial surface are challenged and destroyed by cells of the immune system.
What are most cells in loose connective tissue classified as being?
Transcient wandering cells that migrate from local blood vessels in response to a specific stimuli.
What is dense irregular connective tissue? What is it characterised by?
- abundant fibers
- fibers are typically arranged in bundles oriented in *various directions *
- few cells
- contains mostly collagen fibers
- cells are sparse
- cells are typically of a single type (the FIBROBLAST)
- relatively little ground substance
What is the primary purpose of dense irregular connective tissue? How is this made possible?
providing significant strength (resistant to stretching and stressing):
- because of its high proportion of collagen fibers
What is irregular dense connective tissue?
Dense connective tissue with no order. The collagen fibers are not ordered.
Why are fibers, in irregular dense connective tissue, typically arranged in bundles oriented in various directions
To withstand stresses on organs or structures.
What is type of fiber does the skin contain? What is it called?
fiber: dense irregular fiber
name: RETICULAR layer/deep layer of the dermis
What does the reticular layer provide the skin with?
Provides the skin with resistance to tearing as a concequence of stretching forces from different directions.
What type of layer do hollow organs contain? Why?
Hollow organs possess a distinct layer of dense irregular connective tissue called the SUBMUCOSA.
The fiber bundles in submucosa course in varying planes.
This arrangement of fibers allows the organ to resist excessive stretching and distention.
distention- swelling
What type of movement/stretching can cause damage in the dense irregular connective tissue.
opposite or side direction
What are leather products composed of?
dense irregular connective tissue
What is dense regular connective tissue characterised by?
- ordered and densely packed arrays of fibers and cells
- prominent feature= fibers
- there is little ECM.
What is dense regular conenctive tissue a major component of?
- tendons
- ligaments
- aponeuroses
What are tendons? What do they consist of?
- Cord-like structures that attatch muscles to bones,
- Consist of parallel bundles of collagen fibers.
What is situated between the parallel bundles of collagen fibers in tendons?
TENDINOCYTES: rows of fibroblasts
What are tendinocytes? What is their structure?
Tendinocytes are rows of fibroblasts situated between parallel bundles of collagen fibers.
- surrounded by a specialized ECM that seperates the tendinocytes from the load-bearing collagen fibrils.
How many directions do muscles contract in? What does this relate to?
1 direction only. Fibers of dense regular connective tissues, in tendons, work in the same direction as the muscles.
What is the dense regular connective tissue resistant from?
one direction only (same direction as it is affected when muscle contracts).
What is the “epitendineum”? Are the fibers ordered or not?
the thin connective tissue capsule which surrounds the substance of the tendon.
- collagen fibers are not orderly
What is the “endotendineum”? What is its structure?
- endotendineum is a connective tissue which divides the tendon into fascicles.
- it contains the small blood vessels and nerves of the tendon
What types of connective tissues are prominant in tendons.
most abundant: dense regular connective tissue
also present: dense irregular connective tissue, and loose connective tissue.
What is a ligament?
Cord-like structures that join bone to bone.
What do ligaments consist of?
- fibers
- fibroblasts
arranged PARALLELY.
How do the fibers of ligaments compare to the fibers of tendons?
ligament fibers are less regularly arranged than tendons.
tendon fibers are more parrallely arranged than ligament fibers.
What are aponeuroses? What is their structure? What type of connective tissue is it?
- broad, flattened tendons
- fibers are arranged in multiple layers (instead of lying in parallel rays)
- bundles of collagen fibers in one layer are at a 90 * angle to those in neighbouring planes
- aponeurosis is a dense regular connective tissue as the fibers within each layer is arranged in regular arrays
What is a ‘flattened’ tendon called?
aponeurose
What are the specialized types of adult connective tissues?
- adipose tissue
- reticular connective tissue
- cartilage
- bone
- blood
What is adipose tissue? What does it play a role in?
- specialised connective tissue
plays an important role in: - energy homeostasis: stores energy in lipid droplets in the form of triglycerides.
- hormone production: adipokines (endocrine system)
- immune response: sometimes adipose tissue is associated
What is the name of adipose tissue which is in charge or hormone production?
adipokines
What are the two types of adipose tissue?
1) WHITE (unilocular)
2) BROWN (multilocular)
What is white adipose tissue? Where is it located? What does it do?
- white adipose tissue + collagen fibers + reticular fibers = SUBCUTANEOUS FASCIA
- concenrated in the mammary fat pads (milk glands), and around the skin,
- surrounds several internal organs (kidneys)
secretes a variety of ADOPOKINES eg.:
- hormones (eg. leptin)
- growth factors
- cytokines (immune system molecules)
What are white adipocytes?
- very large cells (over 100 micrometers in diameter)
- single large lipid droplet
cells are very exceptional!!
Where is brown adipose tissue abundant?
abundant in newborns (5% of total body mass).
markedly reduced in adults.
In what animal is the white adipose tissue thick?
a pig
Why do white adipose tissues come out as coloured in the organism? What colour are adipose tissues?
When fat reacts with the environment, it reacts with oxygen, causing it to “rust” become yellow’ish.
What are brown adipocytes?
- smaller than white adipocytes
- contain many lipid droplets
What is the function of brown adipose tissue?
The metabolism of brown adipose tissue generates heat (THERMOGENESIS) by coupling the oxidation of fatty acids in the mitochondria from ATP production.
What is the metabolic activity of brown adipose tissues regulated by? Where is it released from? When?
NOREPINEPHRINE released from sympathetic nerves.
- related to ambient outdoor temperatures
- cold weather increases the amount of brown adipose tissue
Are white adipose tissues empty cells?
No, they may look empty, but they are all filled with one very large drop of fat.
What is a principal difference between white and brown adipose tissue (lipid droplets)?
white: one large droplet
brown: many small droplets
What are the main functions of white adipose tissue? What about brown adipose tissue?
WHITE ADIPOSE TISSUE:
- energy storage
- hormone production
- immune system mediators
BROWN ADIPOSE TISSUE:
- thermogenesis (easily ‘burned’ chemically with a large release of heat)
Where is most brown adipose tissue found?
in newborns
What can adipose tissue undergo?
trans-differentiation
What is trans-differentiation? Where does it occur? What mediated it?
ADIPOCYTES are able to undergo trans-differentiation (brown adipose <–> white adipose)
- this occurs in response to the thermogenic needs of the body
What does cold exposure and physical activity induce?
white-to-brown trans-differentiation of adipose tissues.
What does lack of physical activity and increased food intake induce?
brown-to-white trans-differentiation of adipose tissues.
What is reticular connective tissue? What does it make?
RETICULAR CONNECTIVE TISSUE MAKES:
- the stroma of all lymphatic organs (spleen, lymph node, hemal node, tonsils)
- diffuse lymphatic tissue
- solitary lymphatic tissue
- bone marrow
What is reticular connective tissue composed of?
- STELLATE reticular cells
- star-shaped
- complex three dimentional network of reticulat fibers (similar to mesenchymal cells)
What is reticular connective tissue needed for?
the production of a great, rich, chemical environment for immune system cells to develop and mature.
–> increased protection (antigen production)
