Week 2- Connective Tissue Flashcards
Functions of Connective Tissue
Support, protect, and bind organs
Examples of connective tissue
-Tendons (attach muscle to bone)
-Ligaments (attach bone to bone)
-Adipose connective tissue
-Cartilage
-Bone
-Blood
Similarities between connective tissues
-Share common origin: all derived from mesenchyme (embryonic connective tissue)
-Levels of vascularity
-Range of regenerative capacity
3 Basic Components of Connective Tissue
1) Cells
2) Protein fibers
3) Ground substance
Extracellular matrix
Formed from ground substance and protein fibers
Two classes of cells
1) Resident cells
2) Wandering cells
Resident cells
-Stationary cells that are permanently house within connective tissue
-Support, maintain, and repair extracellular matrix
Types of Resident cells
1) Fibroblasts
2) Adipocytes
3) Mesenchymal
4) Fixed macrophages
Fibroblasts
-Relatively flat cells with tapered ends
-Most abundant resident cells
-Produce fibers and ground substance components of extracellular matrix
Adipocytes
-Appear in small clusters within some types of connective tissue proper
-If large clusters of these cells dominate an area, the tissue is called adipose connective tissue
Mesenchymal
-Type of embryonic stem cells
-If tissue becomes damaged, these cells with divide
-One cell that’s produced replaces stem cell and other cell becomes a committed cell that moves into the damaged area and differentiates into type of connective tissue cell that’s needed
Fixed macrophages
-Relatively large, irregular shaped cells that are derived from monocytes
-Dispersed throughout the matrix where they phagocytize damaged cells/pathogens
-When they encounter foreign material, release chemicals that stimulate immune system and attract wandering cells to tissue
Wandering cells
-Continuously move throughout connective tissue proper
-Components of immune system (primarily types of leukocytes)
-Protect body against harmful agents
Protein fibers
-Strengthen and support tissue
Types:
1) Collagen fibers
2) Reticular fibers
3) Elastic fibers
Collagen fibers
-Unbranched, cablelike, long protein fibers that are strong, flexible, and resistant to stretching
-Comprises about 25% of body’s protein
-Appears white in fresh tissue
-Appear pink when tissue is stained with hematoxylin and eosin
-In many structures such as tendons and ligaments
Reticular Fibers
-Similar to collagen but much thinner
-Contain same protein subunits found in collagen but they’re combined in a different way
-Fiber form a branching, interwoven framework that is tough but flexible
-Abundant in stroma of organs such as lymph nodes, spleen, and liver
Elastic FIbers
-Contain protein elastin
-Fibers branch and rejoin, appear wavy
-Stretch and recoil easily
-Have yellowish color
-Abundant in skin, arteries, and lungs, to allow them to return to their original shape after being stretched
Ground substance
-Molecular (not cellular) material produced by connective tissue cells
-Substance in which connective tissue cells and protein fibers reside
-May be viscous (blood), semisolid (cartilage), or solid (bone)
-Contains different large molecules as well as varying amounts of water
-Glycosaminoglycans (GAGs): polysaccrides that have an attached amino group, have neg charge, hydrophilic; able to attract and absorb water and therefore affect viscosity of ground substance
-Proteoglycan: GAG links to a protein and forms an even larger molecules with the ground substance
Types of Embryonic Connective Tissue
1) Mesenchyme
2) Mucous connective tissue
Mesenchyme
-First type of connective tissue to emerge in developing embryo
-Cells are dispersed within a gel like ground substance that contains fine, immature protein fibers
-Tissue from which all other connective tissues are formed
-Adult connective tissues house numerous mesenchymal cells that act as stem cells to repair damage or injury
Mucous connective tissue
-aka Wharton’s jelly
-immature protein fibers that are more numerous than those in mesenchyme
-only located within umbilical cord
3 Categories of Connective tisaue
1) Connective tissue proper
2) Supporting connective tissue
3) Fluid connective tissue
Connective Tissue Proper Groups
1) Loose
2) Dense
-grouping is based upon relative proportions of cells, fibers, and ground substance
Loose Connective Tissue
-Contains relatively fewer cells and protein fibers than dense connective tissue
-protein fibers are sparse and irregularly arranged
-abundant viscous ground substance
-acts as body’s packing material by supporting and surrounding structures and organs
-subtypes are well vascularized
3 Types of Loose Connective Tissue
1) Areolar
2) Adipose
3) Reticular
Areolar connective tissue
-Unconfined organization of collagen and some elastic fibers
-Highly vascularized
-predominated cell type is fibroblast
-ground substance is abundant and viscous
-present nearly everywhere in the body
-found in skin (papillary layer of dermis and subcutaneous layer that is deep to the skin
-binds skin and some epithelia to deeper tissue
-protects and surrounds organs, some individual nerve and muscle cells, and blood vessels
Adipose connective tissue
-fat tissue
-highly vascularized
-composed primarily of adipocytes
-structure: closely packed adipocytes, nucleus pushed to edge of cell by large fat
droplet, and contains many blood vessels
-2 types: brown and white
-located in subcutaneous layer and surrounding/covering some organs
Brown adipose
-Found in newborns and designed to generate heat
-lost as we age
White adipose
-functions as long-term storage (stores triglycerides), insulation, packing around structures, and a cushion against shocks
Reticular connective tissue
-houses leukocytes and some fibroblasts within meshwork of reticular fibers
-forms stroma (structural framework) of many lymphatic organs (spleen, lymph nodes, and red bone marrow)
Stroma
Structural framework
Dense connective tissue
-Composed mostly of protein fibers and less ground substance than loose
-aka collagenous tissue because collagen is dominant tissue type
-3 categories: dense regular, dense irregular, and elastic
Dense regular
-few fibroblasts, limited ground substance, and abundant collagen fibers that are tightly packed and parallel to one another
-found in tendons and ligaments
-has few blood vessels and takes long to heal after injury due to weak blood supply
Tendons
Attach muscle to bone
Ligaments
Attach bone to bone
Dense irregular
-bundles and clumps of collagen fibers that extend in all directions
-extensive blood supply to collagen fibers
-forms tough sheaths that provide support and resistance to stress in multiple directions
-found in dermis, epimysium (sheath surrounding skeletal muscle), epineurium (sheath surrounding nerve), periosteum (sheath surrounding bone), and perichondrium (sheath surrounding cartilage)
-also forms capsules around some internal organs such as liver, kidneys, and spleen
Elastic connective tissue
-composed of numerous fibroblasts among branching, densely packed elastic fibers
-provide ability for tissue to stretch and recoil
-found in walls of large arteries (like aorta), trachea, and vocal cords
Supporting connective tissue
2 types: cartilage and bone
-forms strong durable framework that protects and. supports soft body tissue
Cartilage
-firm, semisolid extracellular matrix that contains variable amounts of collagen and elastic protein fibers
-cells=chondrocytes
-stronger, more flexible, and more resilient than other connective tissue
-present in areas of body that need support and must withstand deformation like tip of nose and auricle (external part) of ear
Chondrocytes
-mature cartilage cells
-occupy spaces called lucunae
-produce and secrete chemical that prevents blood vessel growth/formation
-cartilage is avascular
-must exchange nutrients and waste products by diffusion with blood vessels
outside
3 types of cartilage
1) Hyaline
2) Fibrocartilage
3) Elastic
Hyaline cartilage
-most common type
-provides flexible support to structures
-named for its clear, glassy appearance
-functions in support
-found in many areas such as respiratory tract (nose, trachea, bronchi, larynx), costal cartilage, and epiphyseal (growth) plates and articular ends of long bones
Fibrocartilage
-weight-bearing cartilage
-resists compression and acts as good shock absorber
-located in intervertebral discs, pubic symphysis, and menisci of knee joint
Elastic cartilage
-resilient and flexible
-found in external ear and epiglottis
-resists deformational pressure
Bone connective tissue
-more solid but less flexible than cartilage
-highly vascularized
-cells=osteocytes (housed in lucunae)
-provide support, serve as levers for skeletal muscle movement, support soft tissues, and protect vital organs
-2 types:compact and spongy
Compact bone
-appears solid but is perforated by neurovascular canals
-formed from osteons which display concentric rings of bone tissue called lamellae (which houses blood vessels and nerves)
Spongy bone
-located within interior of bone
-contains latticework structure of tissue that is very strong yet lightweight
-some houses hematopoietic cells which form a type of reticular connective tissue that makes blood cells (hematopoiesis)
Fluid connective tissue
Blood and lymph
Blood
-composed of formed elements (erythrocytes, leukocytes, and platelets)
-ground substance=plasma which contains proteins and solutes
-erythrocytes transport respiratory gases (O2 and CO2), leukocytes protect body from infectious agents, platelets clot blood, and plasma transports nutrients, wastes, and hormones throughout body
Lymph
-derived from blood plasma bit contains no cellular components or fragments
