basic cell types and epithelia

Question 1

what are the 4 tissues of body

Answer 1

• epithelia (covering)
• connective (support)
• muscle (movement)
• nervous (control)

Question 2

what does epithelia do

Answer 2

• covers the body surface as skin and lines internal cavities and surfaces as a continuous layer

Question 3

what are the general characteristics epithelia have

Answer 3

• 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

Question 4

functions of epithelia

Answer 4

• mechanical protection
• secretion
• absorption
• filtration

Question 5

embryonically where is the epithelium derived from

Answer 5

- ectoderm (epidermis and enamel) 
or endoderm (gastrointestinal and respiratory tracts)

Question 6

different ways in which epithelia can be classified

Answer 6

• number of cell layers
• shape of cell
• specific cell modifications eg, cilia (moves mucus out of airway), microvilli (increase sa more absorption of nutrients)

Question 7

explain number of cell layers (epithelial)

Answer 7

• simple epithelia - have a single layer

- stratified - multiple cell layers

Question 8

shapes of epithelial cell

Answer 8

• cuboidal
• columnar
• squamous (flattened)

Question 9

what is simple squamous and an example

Answer 9

• single flattened layer of cells

- found in alveoli of lungs where a short diffusion distance allows rapid and efficient transfer of respiratory gases

Question 10

where are simple columnar epithelial cells found

Answer 10

• 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

Question 11

why are goblet cells and cilia found in gastrointestinal tracts

Answer 11

• present to maintain a moist environment and trap and remove particulate matter and pathogenic organisms

Question 12

what is stratified squamous and where is it found

Answer 12

• multiple layers of cell, flattened

- tissue is resistant to abrasion and forms the epidermis of skin and epithelium of oral mucosa

Question 13

how many layers above the connective tissue does oral epithelium have

Answer 13

• 4

Question 14

what are the 4 layers in the oral epithelia

Answer 14

• basal
• spinous
• granular
• superficial keratinised

Question 15

what happens in the basal layer

Answer 15

• 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

Question 16

what are the adhesion proteins called between epithelial and connective tissue in oral epithelia

Answer 16

• hemidesmosomes

Question 17

what happens in spinous layer

Answer 17

• cells undergo differentiation - more specific roles and lose cellular features such a nuclei
• cells are linked by desmosomes

Question 18

what do the granular layer cells contain

Answer 18

• contains cells with keratohyalin and membrane coating granules important in waterproofing

Question 19

what does the superficial layer contain

Answer 19

• 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

Question 20

how are glands formed

Answer 20

• when the capacity of epithelium to secrete in not sufficient the epithelium infields to from a structure with a larger sa called glands

Question 21

what is exocrine gland

Answer 21

• communication with epithelium and external environment via a duct

Question 22

endocrine gland

Answer 22

• secretes its products into blood stream

Question 23

role of connective tissue and what is it composed of

Answer 23

• 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

Question 24

what is ECM

Answer 24

• 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

Question 25

what is the ECM of all connective tissues composed of

Answer 25

• 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

Question 26

what are the major cells present in connective tissue

Answer 26

• fibroblasts

Question 27

role and structure of fibroblasts

Answer 27

• 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

Question 28

when a tissue becomes wounded what do fibroblasts differentiate into

Answer 28

• myofibroblasts

Question 29

name different forms of connective tissue

Answer 29

• 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

Question 30

muscle tissue

Answer 30

• muscle - highly specialised to enable contraction, elongated fibres
• types of muscle tissue inc. skeletal, cardiac and smooth

Question 31

nervous tissue

Answer 31

• neurones are highly specialised cells

- enable electric messages to travel over a large distance