Connective tissue Flashcards
Connective tissue
tissue made up of few cells loosely embedded in a complex
Is well vascularized and innervated (most types of CT)
Connective Tissue Functions
Connects other tissues Gives form, subdivides organs Supports body (bone tissue) Thermoregulation Nutrition and storage Defense and repair mechanisms
CT relevance
Basic understanding of tissue organization development and functioning Trauma and healing Inflammation Edema Vit C déficiency Tumor terminology and development
Fibroblast
Resident cell
The most numerous cell population of CT
They synthesize the fibers of the CT: collagenous, elastic, and reticular
Resident cell
A cell population that stays in the connective tissue
Reticulocytes
Resident cell
Special fibroblasts that synthesize a fine type of collagen fibers that offer scaffolding to the parenchyma (specialized epithelial cells) of various organs (lymph nodes, spleen etc)
Parenchymatous organs do need support for their internal organization but are not subjected to high mechanical stress
Adipocytes
Resident cell
Cells specialized in depositing lipids
Can be of 2 types: multiocular (contain multiple droplets-brown) and uniocular (a single bug round drop of lipids-white)
Macrophages
Resident cell
Resident phagocytic cell of CT (fixed or mobile)
Monocytes from blood cross the vessel walls into CT becoming macrophages
Tissue macrophages can proliferate locally; they survive for months
Janitors of CT
named by location (Kupffer cells = macrophages in liver
Irregular shape, round nucleus
Mast cells
Resident cell
Cells filled with basophil granules
They are involved in inflammatory and allergic reactions
Degranulation of mast cells causes release of histamine and other chemical mediators that trigger symptoms of allergy
Transient CT cells
= WBCs
Collagen fibers
The most numerous fibers of CT
Composed of fibrils usually arranged in bundles of indefinite length
Are white; a large number of collagen fibers gives a white color to collagen rich tissue: tendons, tunica albuginea, sclera of eye etc
Very high tensile strength, very strong, can only stretch 5% of initial length
Collagen as a substance
The most abundant protein in the body representing 30% of its dry weight in humans
Many cells synthesize collagen- fibroblasts, chondroblasts, osteroblasts
Procollagen is formed in the fibroblast, transported outside the cell and then assembled into collagen fibrils
Vitamin C is an important cofactor in collagen synthesis
Elastic fibers
Individual, branching and anastomosing fibers
Might stain purple in HE but hard to detect; more evident with special stains
0.2-5 um diameter in loose CT
yellow in natural color
Can stretch 2.5 times original length and recoil
Found in aorta and elastic arteries, lungs, vocal cords, dermis, pinna of ear, epiglottis etc
Reticular fibers
Form a fine network (reticulum) that can be stained by silver
Are type 3 collagen, synthesized by reticular cells, liver cells, smooth muscle cells and skeletal muscle cells.
Serve as a scaffolding to cells or cell groups of various organs
Ground substance
Amorphous gel-like bathed in interstitial fluid
Produced by resident cells
Composed of:
-glycosaminoglycans (GAGs)
-proteoglycans
-glycoproteins
Properties of these molecules allow for binding of water, resisting compressive forces, cell adhesion to fibers, cell migration, barrier to bacterial/venom penetration
Interstitial (tissue) fluid
A solution of nutrients and dissolved gases derived from plasma
Bathes the cells, fibers, and ground substance, aids in removing waste
Fluid dynamics maintain proper balance in CT
Tissue fluid determines skin turgor; a decrease in skin turgor is a late sign of dehydration
Lymphatics are important in fluid movement and prevention of edema
Not visible on slides
Edema
Abnormal accumulation of tissue fluid
Loose and Dense irregular CT
Loose: lots of cells, few fibers that are usually are to see
Dense: few cells, many thick collagen fibers, irregularly packed
Dense regular CT
Fibrocyte nuclei visible (very thin and elongated)
Parallel arranged collagenous fibers
Very stron, resists tensile forces
Found in tendons, ligaments, cornea
Reticular CT
Network of fine collagen fibrils =reticular, offering support for cells
Usually synthesized by reticulocytes, reticular CT is observable in lymphatic organs (except thymus) and spleen
It formed the stroma in lymph nodes (dividers for the mass of functional tissue-parenchyma)
Adipose CT
Composed of adipocyte: fatty cells with basement membrane
Functions
-Energy storage
-endocrine: adipocytes produce leptin, which has regulatory effect on body fat. Leptin levels are proportional to body fat. It signals to the brain that the body has had enough to eat
When adipocytes outnumber other cell types –> adipose tissue
White adipose tissue
Morphology: unilocular fat cells- one lipid droplet
Functions: energy storage
Insulation
Endocrine=hormone “leptin” secretion
Brown Adipose Tissue
Morphlogy: multiocular fat cells- several lipid droplets; many mitochondria
Found in hibernating and newborn animals
Function: heat generation
