Histology Flashcards
(152 cards)
What is Histology?
The study of tissues
What is the importance of tissues
Increase the efficiency of an organism by division of work
What are the characteristics of cells in a tissue?
- Generally share a similar origin in the embryo
- They may be of same type or of different type
- Share a similar function
- They are physically linked
What is an organ?
A number of tissues working together as a functional unit
What is a system?
A functional unit of organs
List plant tissues
- Parenchyma
- Collenchyma
- Schlerenchyma
- Xylem
- Phloem
List animal tissues
- Epithelial tissues
- Connective tissues
- Muscle tissues
- Nervous tissues
What is the most common characteristic of all parenchyma?
They are living tissues
Describe the structure of parenchyma
- The cells are living
- The cells are roughly spherical or elongated
- The cells have thin cellulose cell walls
- The cells have a large central vacuole
- The cytoplasm and nucleus of the cells are peripheral
- Made up of tightly packed cells
- The cells have large intercellular spaces
- It is made up of one type of cell
Give the functions of parenchyma
-Provide support to the plant
-Gaseous exchange
-Store food
-Exchange materials eg water, oxygen, carbon dioxide etc
-Allow growth of the plant
-Passage of water and mineral salts
Give the adaptations of the parenchyma to its function
- The cells have thin, permeable cell walls that allow exchange of mater eg water, mineral salts, glucose, oxygen and carbon dioxide etc
- The cells are closely packed giving them mechanical strength which provides support to the plant
- The cells have a concentrated central vacuole which is osmotically active thus providing support via turgidity in herbaceous plants
- The large central vacuole of the cells provides adequate space for food storage in the plant
- The cells have numerous large intercellular spaces making it suitable for gaseous exchange
- The parenchyma is made up of unspecialized cells thus it can perform a variety of functions
- Parenchyma is made up of living cells which allows growth
- The parenchyma are tightly packed which enables them to act as packing tissue in plants
Where is parenchyma tissue found?
- Rays in woods
- Cortex
- Packing tissue in xylem and phloem
- Pith
Describe the structure of the epidermis
- One cell thick
- Living
- Cells are elongated
- Cells are flattened
- Tightly packed cells
- Transparent
- Has a waxy cuticle; a waterproof layer of cutin
What are the functions of the epidermis as a modified parenchyma?
- Protection of the plant from desiccation and infection
- Allow light to reach the palisade cells for photosynthesis
What name is given to the layer of cells that replaces the epidermis when it wears out?
Cork layer/ cork cells
Describe the structure of the guard cells
- Have pores called stoma
- Contain chloroplasts
- Occur in pairs
- Each cell is bean shaped
- Inner layer is thicker than outer layer
What are the functions of the guard cells as modified parenchyma?
- Control the opening and closing of the stomata
- Allow gaseous exchange
- Control transpiration
- Site for photosynthesis
Where are guard cells found?
- Leaf epidermis
- Stems especially herbaceous
Describe the structure of hair like extensions
- Unicellular or multicellular
- May be hooked
What are the functions of the hair like extensions as modified parenchyma?
- Aid in seed dispersal
- Absorb water and mineral salts for plants
- Reduce water loss
- Protection
- Promote cross pollination
- Feeding in carnivorous plants
Where are hair like extensions found?
- Roots
- Climbing plants
Describe the structure of the glandular cells
- May be hair like
- Have glands
What are the functions of the glandular cells as a modified parenchyma?
- Secretion of sticky substances
- Secrete enzymes for digestion and absorption of food in insectivorous plants
Where are glandular cells found?
- Insectivorous/ carnivorous plants