Connective Tissue Flashcards
Connective Tissue
most abundant tissue type weight
Some Systems are almost entirely connective tissue
Some Systems contain very little
All Connective tissue has 3 components
1.) Ground substance
2.) Extracellular fibers
3.) Specialized Cells
Ground Substances
Found in CT
IS an amorphous, homogenous material that ranges in texture from a liquid/gel to a calcified solid
Ground substance in soft CT
-Composed of unbranched chains of glycoproteins (glycosaminoglycans or GAGS) - Most common is Hyaluronic acid combined with 2 % protein - Large molecules help orient the formation of fibers
- is medium through which cells exchange nutrients and waste with the blood stream
-Shock absorber
-protects more delicate cells
-Thick texture makes it an obstacle for pathogens - Produce hyaluronidase - Degrades hyaluronic acid and enables microbe (pathogen) to move through tissue easier
Extracellular fibers
Three types - Collagenous, Reticular, and Elastic
Collagenous Fibers
-Strong, thick strands composed of structural protein collagen
-Organized into discrete bundles of long, parallel fibrils - Fibrils are composed of microfibrils
-Posses a tremendous amount of tensile strength - resists pulling forces - Found in tendons and ligaments
-Fiber itself is white - Tightly packed bundles are also white - Sometimes known as white fibers
- Density and arrangement - Varies depending on function of tissue as a whole - can range from loose (Surrounds and protects organs) to Dense (Seen in tendons / ligaments)
Reticular Fibers
-Composed of collagen protein
-Not as thick as collagenous
-Thin, delicate, branched into complex networks - “Mist net” - Provides support for highly cellular organs (Endocrine glands, lymph nodes, spleen, bone marrow, and liver), also found in blood vessels (prevents aneurysms), nerves, muscle fibers, and capillaries
Elastic fibers
-Composed primarily of the protein elastin
-Branched and form complex networks - lack tensile strength of collagenous fibers
-Composed of bundles of microfibrils - they are coiled
-Can stretch and contract - like a rubber band
-Occur in tissues that are subject to stretch (vocal cords, lungs, skin, blood vessel walls)
-Due to the yellow color, can be referred to as yellow fibers
Specialized Cells
Two categories
Fixed - remain in CT, involved in the production and maintenance of the matrix
Transient - Pass in and out of CT, involved in the repair and protection of tissues
Fixed cells
Most noteworthy one: Fibroblast
fat cells
Reticular cells
Fibroblasts
-Large, irregular shaped
-Manufacture and secrete both fibers and ground substance
-Reproduce - Metabolically very active
-Each type of CT is characterized by a predominant fibroblast - Cartilage (Chondroblasts), Bone (Osteoblasts) - As cell mature, they become less active - when this happens they adopt the suffix -cyte (Chondrocyte, osteocyte, fibrocyte)
Fat cells
-Adipose cells or adipocytes
- Young cells - resemble fibroblasts
-As they mature - they fill with lipids and increase in size - Nuclei are pushed to one side
-When in groups - Adipocytes become adipose tissue
Reticular cells
-Flat, star-shaped cells - long outreaching arms that tough other cells - form netlike connections throughout the tissue they compose
-Function is debated - Most agree that they help with immunity and manufacture reticular fibers - Part of the immune system (Lymph nodes, spleen, Bone marrow)
Transient (Wandering Cells)
-Many different types
-Three common types - Leukocytes, Mast cells, microphages
-All are WBCs
Leukocytes
-Found in the blood ad move into CT when inflammation or infection is present
-Bigger than RBCs - Can squeeze through tiny walls through a process called diapedesis
-important members of immune system
-Five diff types - Most protect the body by engulfing and digesting pathogens - Others make antibodies that attach to pathogens and destroy them
Mast Cells
- Oval cells that are easily identified by the large numbers of dark-staining granules in cytoplasm - the granules contain heparin and histamine
-Biochemicals that start an inflammatory response
-Histamine - increases blood flow - make capillaries leaky
-Heparin - Prevents clotting - makes sure blood flow is increased
Macrophages
-Massive, irregular cells
-Phagocytizing scavengers (cleaning crew)
-Breakdown pathogens via lysosomes
Types of CT : Connective tissue proper
- Largest classification and contains every subtype of CT except Bone, Cartilage, and Blood
- Two subclasses
—Loose CT - Areolar, Adipose, and Reticular
—Dense CT - Dense regular, Dense irregular, Elastic
Loose CT: Areolar Tissue
-Tangle of randomly placed fibers and cells suspended in a thick, translucent ground substance
-Appears relaxed with a massive number of round and star-shaped cells among crisscrossing fibers
-predominant cell - fibroblast - Large spindle-shaped cell that makes elastic, reticular, and collagenous fibers
-Most Common CT
—Found Everywhere
—Acts as packing material - supports and cushions delicate structures; forms a subcutaneous layer; envelops blood vessels, nerves, and lymph nodes; Present in all mucous membranes (As the Lamina propria and submucosa)
—Ground substance of areolar tissue - Mainly composed of hyaluronic acid (nutrients and waste are easily transported) - Some WBCs produce hyaluronidase (breaks down matrix for easier movement, some pathogens doe this as well)
Adipose Tissue
-Commonly known as fat - Adipose cells predominate
-Acts as a shock absorber - kidneys
-Acts as insulation
-Two main types - White adipose and brown adipose
White Adipose
- Found throughout the body - Deep layers of skin
-Cells are large and filled with lipid - Single large droplet
Brown Adipose
- Found in newborns and hibernating animals
-Highly specialized adipose tissue
-Important in temp regulation
-site of heat production
-energy derived from the oxidation of lipids and released from electron transport is dissipated as heat* (Rather than ATP)
-Contains high number of mitochondria - Oxidation causes cytoplasm to be darkly stained - henced the name brown fat
-Also lipid filled - Lipids are stored in multiple small vesicles rather than in a single large droplet
Reticular CT
-Composed of a 3-D network of thin reticular fibers
-Resemble Areolar CT - Loosely arranged fibers and many fibroblasts suspected in ground substance - Differs because it is only composed of one type of fiber (reticular fibers)
-Forms a network called stroma - Makes up framework of several organs - liver, spleen, lymph nodes, and bone marrow
-found in a limited number of sites
Dense Fibrous CT
Densely placed arrangement of collagen fibers. Little space available for ground substance and cells
Three main types - Dense regular, Dense irregular, Elastic
Dense Regular CT
-Tightly packed parallel collagen fibers
-Lie in the direction of the force exerted on them - Overall tissue had tremendous tensile strength - but only in one direction
-Appears silvery or white
-Avascular - slow to heal
-Makes up tendons and ligaments
-Also makes the broad, fibrous ribbons that cover muscle or connects them to other structures
-Can be found in fascial sheets that cover muscles - sheets are stacked into layers, one on top of another - they may not run in the same direction, this helps to create an overall structure (fascia***)- can withstand forces from more than one direction
Dense Irregular CT
-Primarily composed of collagen fibers that are arranged in thicker bundles than those found in Dense regular CT
-Fibers are interwoven randomly to form a single sheet that can withstand forces from many diff directions - Found in the dermis - Fibrous coverings of organs (Kidney, testes, liver, spleen
-forms tough capsules of organs
Elastic CT
-Ligaments stretch more than tendons - have a higher number of elastic CT (nuchal ligament)
-Found in few regions- Spaces between vertebrae in spine - regions that require stretching (artery wall, stomach, bronchi, bladders, regions of the heart)
Specialized CT
cartilage, bone, blood
Cartilage
-more rigid than dense CT, but is ore flexible than bone - found in joints
-function - prevents the sensitive layer of bones from rubbing against one another
- does not contain nerves - can tolerate a large amount of compression without causing pain
-composed of cells and matrix - cells: chondrocytes (live in hollowed out pockets in the matrix - Lacunae) and ground substance (firm gel containing two diff types of GAGs and an adhesion protein (chondronectin) (chondroitin sulfate and hyaluronic acid)
-Avascular - recieves nutrients from the perichondrium
-Three types based on the type of fiber in the matrix - Hyaline, elastic, and fibrocartilage
Hyaline cartilage
- Most common
- Closely packed collagen fibers
- Found as articular cartilage
a. —At the ends of long bones in joints
b. —Connects ribs to sternum
Elastic cartilage
-Similar to hyaline - But contains many elastic fibers - Form dense, branching bundles (Appear black microscopically)
-Can withstand repeated bending -Found in epiglottis, larynx, pinnae (ears)(standing ears in dogs)
Fibrocartilage
-Found merged with hyaline cartilage and dense CT
Contains - Thick bundles of collagen fibers - Has fewer chondrocytes and lacks a perichondrium
-Can withstand much pressure - Found in joints of spine, Knee, Pelvic girdle
Bone
-Hardest and most rigid CT
-Specialized matrix - Combination of organic collagen fibers and inorganic calcium salts
-Well vascularized - Haversian Canal - Contains vascular and nerve supply
Blood
-Most atypical CT
-Liquid matrix - Plasma
- Fibrous matrix - Array of protein molecules suspended in solution and visible only when blood clots
Membranes
-Composed of epi tissue bound to underlying CT
-Thin, protective layers that line body cavities, separate organs, and cover surfaces
4 types - Mucous, serous, cutaneous, synovial
Mucous (Mucosae)
-Characterized by position - Found lining the organs that have connections to the outside environment (Digestive, rep, urinary, repro)
-Composed of Epi layer and lamina propria - Epi layer in mucous membranes - stratified squamous or simple columnar - covers the loose CT (Lamina properia) - submucosa (Connects the mucosa to underlying structures)
-Usually produces large amounts of protective/lubricating agents - goblet cells - produces mucous (water, electrolytes, and a protein mucin)
-Same can absorb - mucosal layer of intestine
Serous (serosae)
-Lines walls and cover organs that fill closed body cavities
-Characterized by: continuous sheet that is doubled over to form 2 layers with a narrow space in between - Cavity wall = parietal - outer surface of organs = visceral layer
Serosa
-Composed of a sheet of simple squamous epi bound to an underlying layer of loose CT
-The organization allows a great amount of permeability and enables interstitial fluid to pass through the membrane into the narrow spaces between the serosal layers
-serosal fluid - a transudate - thin and watery - contains electrolytes but no mucin - coats the parietal and visceral layers (moist slippery surface which reduces friction between organs)
-Serosa fluid takes on diff. names depending on where they are located: Thorax = Pleural fluid - Abdomen = peritoneal fluid - Surrounding the heart = pericardial fluid
Cutaneous (integumemt)
-Organ that is perpetually exposed to the outside environment
-Composed of: Keratinized stratified epi and keratin
Keratin: a waxy substance that fills the cell of the epidermis layer, responsible for the waterproof quality of the skin, aids in the prevention of desiccation (keeps it dry), durable (withstands abrasions)
-Attached to the underlying layer of dense irregular CT (dermis) - Rich in collagenous, reticular, and elastic fibers
Synovial
-Lines the cavities of joints - no epithelium - composed exclusively of CT
- Gross appearance - smooth, shiny, and white
-Histologic appearance - Composed of loose CT and adipose tissue covered by a layer of collagen fibers and fibroblasts
- Produce synovial fluid - fills joint spaces with **hyaline cartilage ** - reduces friction and abrasions at the ends of the bones
