Tissues: Structure & Function Flashcards
Tissues
Formed by many cells that act together to perform a comprehensive function.
Have varied structure and functions
Organs
Two or more tissue types that combine
Four tissue types
- Muscle
- Nervous
- Epithelial
- Connective
Epithelial tissues
Act as selective barrier Absorption function Covering function Secretes mucus Avascular (relies on CT vascularly) > Named for size and shape
Muscle tissues
Specialized to contract
Connective tissues
> Mostly referring to fibrous types
Underlies and anchors the epithelial tissues
Found in the skin (dermis)
Surrounds and supports internal epithelial, muscle, and nervous tissues
All fibrous CT contain collagen in extracellular matrix
Function of connective tissues
SUPPORT Underly and anchor tissue Connect Protect (physical barrier, sometimes to prevent infection spreading) Structural connections Provide nutrients Immune function
Characteristics of connective tissue
Components include:
Cells, fibers, & ground substance
Composed mainly of extracellular matrix (fibers & g.s.)
Highly vascular (except cartilage)
Connective Tissue Proper
Has more collagen type I than anything else
All have collagen in the extracellular matrix
Contains fibers in it’s extracellular matrix
Two basic types: dense & loose
Specialized connective tissues (types)
Elastic tissue Hematopoietic tissues (lymphatic, myeloid) Mucous tissue Blood Cartilage Bone Articular cartilage
Extracellular matrix
Complex structure that includes fibrous proteins, proteoglycans (g.s.) and glycoproteins.
Contains fibroblasts that bind to elements of the g.s. and glycoproteins
“All of the stuff that CT make” - depends on each type functionality
Fibroblasts
Produces collagen and other fibers
Binds to elements of the g.s. and glycoproteins, such as laminin and fibronectin
Glycoproteins
A sugar protein compound
Function: structure & binding cells to framework
(usually end in suffix -nectin)
Ground substance
Helps make up extracellular matrix
Mix of proteoglycans that are formed by a large protein molecule that bonds to a glycosaminoglycan (GAG).
Proteoglycans can swell with water (they’re hydrophilic) and attract ions.
Structure is viscous (very important) and acts as a chemical and physical barrier
GAG’s
Glycosaminoglycan’s
Highly negatively charged, provide the incentive for a proteoglycan to attract water.
Hydrophilic and swell
ex: Hyaluronic acid, is a specific GAG.
Hyaluronic acid
A specific type of GAG.
Found in hyaline cartilage
When bound to a protein to form a proteoglycan, is particularly hydrophilic and gives hyaline cartilage g.s. it’s great ability to withstand compression without inhibiting flexibility.
Fibers/Fiber proteins
Help make up extracellular matrix
Long, slender protein polymers
3 main types: collagen, reticular, elastic
Collagen
Varies in mechanical properties
Great at resisting tension!
5 Types
Reticular Fibers
Especially thin and often form a net-like mesh network
Produced by fibroblasts
Found in/around structures subject to shape change (abdominal organs)
Provide supporting framework for tissue or organ
Consist of Collagen Type III fibrils
Support lymphatic organs
Elastic Fibers
Made of elastin
Found in varying amounts in different CT
Can stretch up to 150% their resting length
Respond to stretch and distention without losing shape
Organized in sheets
Produced by fibroblasts
Consist of central core of protein elastin (dense concentrations are in walls of large arteries) and glycoprotein fibrillin
Found: Very dense in artery walls, ligaments of spinal column, and laryngeal cartilages.
Types of Collagen
5 Types of Collagen:
Type I, Type II, Type III, Type IV, Type V
Type I Collagen
Most abundant type
Forms fibers
Found in CT proper, bone, dentin, tendons, and organ capsules
Responsible for preventing fractures bone
Type II Collagen
Exists as thin fibrils
Resists tension, but fibril diameter is small!
Found in hyaline and elastic cartilage
Type III Collagen
Mainly found in reticular fibers
Good in organizing deformation (like a sponge, forms an interlocking maze but will return to form)
Cellular components of CT
Fibroblasts Macrophages Mast Cells Plasma Cells Leukocytes Adipose cells
Fibroblast
Most common type of cell in CT
Makes collagen plus both elastic & reticular fibers
Make carbohydrates found in g.s. AND secreting most other components into extracellular matrix
Found: in ligaments, dermis,
Macrophages
Phagocytic cells derived from monocytes
They can act defensive (phagocytosis of bacteria) or normal (phagocytosis of cell debris)
Mast cells
Cells are filled with granules
Stored in mediators of inflammatory response
Release of their granules results in hypersensitivity, allergy, and anaphylaxis
Primary substances found in mast cells:
Histamine & Heparin
Plasma cells
Found in loose connective tissue where antigens tend to enter the body (primary GI & respiratory tracts)
Produces only type of protein (one specific antibody)
Leukocytes
White blood cells;
Consist of neutrophils, eosinophils, basophils, lymphocytes and monocytes.
Type depends on location in body
Adipose cells
Specialized CT tissue cells that store fat
Found in loose CT
Histamine
Found in mast cells
increases permeability of small blood vessels
Causes edema in surrounding tissue
Increases mucus production (bronchi)
Triggers smooth muscle contraction in pulmonary airway
Heparin
Found in mast cells
Is an anticoagulant
Loose CT Generally Location Components Characteristics
“Areolar” tissue
Most common type of CT cells - everywhere!
Found in dermis, hypodermis, around blood vessels and serous linings.
Contains fibroblasts & macrophages,
Contains collagen types, elastic fibers & reticular fibers
Fluid g.s.; most fluid
Flexible but not resistant to injury (has more elastic fibers than dense)
Well vascularized and may contain adipose cells
Have sites of microvasculature
Sub category of CT Proper
Hypodermis
Fatty layer deep to the skin
Dense CT
Generally
Not flexible, but better at resisting injury
Lots of type I collagen, that is BUNDLED
Good amount of elastic fibers, not much reticular
Sub category of CT Proper
Dense Regular CT
Lots of parallel-arranged bundles, tightly packed, running in same direction Extremely resistant to tension Occurs in sheets, bands, or cords Heavily eosinophilic Ex: tendons, ligaments
Dense Irregular CT
Collagen fibers arranged in bundles, but not organized in particular direction
Resists stresses in all directions, good at resting shear
Found in dermis, periosteum & perichondrium, & organ capsules
Elastic CT
Another type of fibrous CT
Relatively rare by itself (lig. nuchae) but often mixed with other tissues
Elasticity
Ex: tunica media
Reticular CT
Another type of fibrous CT
Provides stable framework (stroma) within organs;
Ex: parenchyma mixed within meshwork
Tendons
Connect muscle to bone
Very dense collagen bundles with heavy concentrations of fibroblasts
Ligaments
Connect bone to bone
Very similar to tendons but the collagen bundles are more randomly arranged
“Primative”
not very advanced
can refer to cells, embryo, etc.
Mesenchyme
product is very watery
some primitive CT tissue with interstitial fluid
appears like scattered slender star-shaped cells
Cartilage
type of CT
still fibrous internally
functions to resist tension/forces
Inflammation
Occurs in fascia
CT compartmentalizes to minimize effect
Sets the stage for repair
Myofibroblasts
Sub group of fibroblasts
have contractile properties
specialized to act during wound contraction (healing)
Monocytes
Bloods cells that migrate from the blood stream into CT
Give rise to macrophages
Neutrophils
Most popular type of WBC
Functions:
Bacterial defense, acute inflammation, some clean up.
Found in dermis,
Basophils
Type of WBC
Act similar to mast cells
Circulate and occasionally migrate out
Lymphocytes
Type of WBS
Two types:
T Lymphocytes
B Lymphocytes
Appearance of Loose CT
*picture
A scattered view of cells
Thick collagen fibers, wavy elastic fibers, mast cells
Grossly appears as web of fibers
Basic function of Loose CT
Supportive
Also, nutritive, protective
