Epithelia And Connective Tissue Flashcards
Characteristic features of epithelium
Forms dense cellular sheets (cells attached to each other via desmosomes, adherents junctions)
Has no blood vessels (relies on diffusion from blood)
Sits on basal lamina complex (separates epithelium from underlying connective tissue to provide support and attachment between them)
Classification of an epithelium
Cell shape (squamous, cuboidal, columnar)
Cell arrangement (stratified, simple, pseudostratified)
Cell specialisations (cilia, microvilli, keratinisation)
Specialised cells present (goblet cells)
Locations of simple squamous
Lines surfaces involved in passive transport of gases (lungs), fluids (endothelium of capillaries)
Locations of simple cuboidal
Lines small ducts and tubules, collecting tubules of the kidneys, small excretory ducts of salivary glands and pancreas
Location of simple columnar
Often absorptive surfaces (small intestines), secretory surfaces (stomach)
Microvilli
Function
Size
Structure
Increase SA for absorption
0.5-1um long
Shape maintained by actin anchored to cell membrane
Base of actin filaments form part of terminal web, linked to intermediate filaments
Describe goblet cells
Modified columnar epithelial cells that synthesise and secrete mucus (glycoproteins stored as granules)
Found in many epithelial linings in the respiratory and GI tract
Stains poorly with H and E
Location of pseudostratified columnar epithelium
Lines upper respiratory tract (trachea, bronchi, bronchioles)
Cilia
Function
Size
Structure
Motile structures for moving fluids and particles along epithelial surface
7-10um
At the top of the cilia, central MT pair surrounded by 9 pairs of MT
At the basal body of the cilia, 9 MT triplets surround central core
Purpose of stratified epithelium
Physical protection in oral cavity, pharynx, oesophagi, anal canal, uterine cervix
Sites subject to mechanical abrasion, kept moist by glandular secretions
Nucleated cells
Location of keratinizaed stratified squamous
Physical protection, prevent desiccation
Top layer composed of dead enuculeated cells
Keratinisation
Function
Protection from UV, thermal, chemical, mechanical sources
Prevention of desiccation
- cells become squamous
- keratinisation cross linked by S-S bridges
- cells die, lose nuclei and other organelles, become dehydrated, packing keratin filaments together
Structure of skin in layers
Function of each layer
Stratum corneum (only keratin found here) Stratum granuloum (many keratinohyalin granules containing keratin found here) Stratum spinosum (many desmosomes here to prevent tearing) Stratum basale (mitosis and renewal of keratinocytes)
What cells are found in the transitional epithelium
Function of cells here
Stratified epithelium, only in urinary tract
- Distention, accommodate large degrees of stretch
- Protection, from toxic content
- Waterproof, prevent water leaking into conc urine
Nucleated cells, more rounded than surface stratified epithelium
Functions of connective tissue
Forms architectural support framework of body, preserve body form
- Filler for space between other tissue types
- Structural support
- Attachment
- Physical protection
- Defence via immune cells
- Condiut for blood vessels and nerves
- Lipid store
- Wound healing
Soft connective tissue properties
Organ capsule
Tendons and ligaments
Areolar, adipose tissue
Phagocytise, immunocompetent cells
Physical barrier preventing transport of microorganisms that pass through epithelial
Nutrient role
Examples of hard connective tissue
Bone
Cartilage
Composition of soft connective tissue
Major constituent = ECM (GAGs, protein fibres, scattered cells, tissue fluid)
Consistency depends on properties of components, can vary
Cell of the connective tissue
Permanent cells (fibroblasts, adipocytes)
Transient cells (mast, plasma, leukocytes, lymphocytes)
Function of fibroblasts
Synthesise collagen and ground substance
When mature, nuclei condense, elongate with sparse cytoplasm
Active fibroblasts have more cytoplasm w RER and Golgi
Function of adipocytes
May be isolated/small groups within connective tissue
Largest energy store in body
In continuous turnover and sensitive to hormonal, nervous stimuli
Deposits in form of pads (shock absorber)
Fill spaces between tissues, help keel tissues in place
Structure of proteolysis S
Have a protein core (core protein), GAG side chains
Properties of collagen
Inelastic tensile strength (flexible and strong)
In parallel arrays forming bundles
Properties of elastic fibres
Stretchable, resilient fibres and sheets
Hydrophobic, assembles by cross linking
Made from tropoelastin which polymerises in ECT
Microfibrils of structural glycoproteins fibrillation incorporate in elastin => form fibres
Types of soft connective tissue
Basal lamina
Loose
Dense
Structure and location of loose connective tissue
Abundant elastic fibres and collagen bundles embedded in ground substance
Component of lamina proprietary of GI and resp tract and hypodermics
Classification of dense connective tissue
Subclassified according to orientation of collagen fibres as irregular and regular
Location of irregular dense connective tissue
Dermis of skin, irregular arrangement of collagen fibre bundles
Consists of papillary and reticular layers
Function of the papillary layer of the dermis
Very folded to strengthen the connection between the epidermis and dermis
Abundance of capillary loops, nerve fibres, Meissner’s corpuscles (light touch)
Function of the reticular layer of the dermis
Densely packed with collagen, elastic and reticular fibres
Give the dermis strength, elasticity and extensibility
Location of regular dense connective tissue
Tendons, ligaments, regular parallel bundles of collagen fibres separating linear rows of fibrocytes
Large amount of colllagen for tensile strength, stop overstretching
