basic cell types and epithelia Flashcards
what are the 4 tissues of body
- epithelia (covering)
- connective (support)
- muscle (movement)
- nervous (control)
what does epithelia do
- covers the body surface as skin and lines internal cavities and surfaces as a continuous layer
what are the general characteristics epithelia have
- exist as a continuous sheets of densely packed cells with minimal extra cellular matrix
- these tissues are avascular (no blood vessels)
- therefore rely on underlying connective tissue for supply of nutrients and physical support
- they can be polarised - where individual cells have a difference between their basal end and apical surface
functions of epithelia
- mechanical protection
- secretion
- absorption
- filtration
embryonically where is the epithelium derived from
- ectoderm (epidermis and enamel) or endoderm (gastrointestinal and respiratory tracts)
different ways in which epithelia can be classified
- number of cell layers
- shape of cell
- specific cell modifications eg, cilia (moves mucus out of airway), microvilli (increase sa more absorption of nutrients)
explain number of cell layers (epithelial)
- simple epithelia - have a single layer
- stratified - multiple cell layers
shapes of epithelial cell
- cuboidal
- columnar
- squamous (flattened)
what is simple squamous and an example
- single flattened layer of cells
- found in alveoli of lungs where a short diffusion distance allows rapid and efficient transfer of respiratory gases
where are simple columnar epithelial cells found
- lining gastrointestinal tracts
- sa and absorption increased due to presence of microvilli and also have goblet cells
- the orientation of the cells are in contact with the basal layer they do not all reach the surface
- referred to as pseudostratified
why are goblet cells and cilia found in gastrointestinal tracts
- present to maintain a moist environment and trap and remove particulate matter and pathogenic organisms
what is stratified squamous and where is it found
- multiple layers of cell, flattened
- tissue is resistant to abrasion and forms the epidermis of skin and epithelium of oral mucosa
how many layers above the connective tissue does oral epithelium have
- 4
what are the 4 layers in the oral epithelia
- basal
- spinous
- granular
- superficial keratinised
what happens in the basal layer
- where cell division occurs to supply replacement cells
- cells are attached to a ECM called basal lamina (basement membrane) forming junction between epithelial layer and connective tissue
what are the adhesion proteins called between epithelial and connective tissue in oral epithelia
- hemidesmosomes
what happens in spinous layer
- cells undergo differentiation - more specific roles and lose cellular features such a nuclei
- cells are linked by desmosomes
what do the granular layer cells contain
- contains cells with keratohyalin and membrane coating granules important in waterproofing
what does the superficial layer contain
- contain dead cells
- in oral cavity has a thick layer of keratin to act as a protective barrier to abrasion
- in areas such a buccal mucosa epithelium needs to be more flexible so keratin layer is absent
how are glands formed
- when the capacity of epithelium to secrete in not sufficient the epithelium infields to from a structure with a larger sa called glands
what is exocrine gland
- communication with epithelium and external environment via a duct
endocrine gland
- secretes its products into blood stream
role of connective tissue and what is it composed of
- provide a structural framework for the body
- connective tissue hold together body cells, tissues and organs and provide protection for them
- all connective tissue are composed living cells embedded in ECM
what is ECM
- non living
- non cellular component that is secreted by connective tissue cells
- connective tissue contain much fewer cells than epithelial which are separated from each other by ECM
what is the ECM of all connective tissues composed of
- fibrous proteins eg collagen embedded in ground substance
- each connective tissue has an ECM with a unique composition and structure which is essential to its functions
what are the major cells present in connective tissue
- fibroblasts
role and structure of fibroblasts
- main job is to maintain the ECM and provide structural and nutrient support to nearby cells such as epithelium
- it is a long, thin cell with protrusions
when a tissue becomes wounded what do fibroblasts differentiate into
- myofibroblasts
name different forms of connective tissue
- loose - packing and insulation
- dense - tough, fibrous for protection and attachment
- cartilage - semi rigid allows flexibility, lots of matrix, hyaline most common
- bone - protection of underlying organs , base for muscular activity
muscle tissue
- muscle - highly specialised to enable contraction, elongated fibres
- types of muscle tissue inc. skeletal, cardiac and smooth
nervous tissue
- neurones are highly specialised cells
- enable electric messages to travel over a large distance
