Tissue: a group of similar cells with a shared function
There are four main categories of animal tissue:
- Epithelial tissue: covering layer of tissue for the outside of body and on internal organs and cavities within body – functions in protection, absorbing, and/or secretion depending on location, e.g. skin, kidney and gland tubules, blood vessels (capillaries, arteries, veins) and mucous membranes of the respiratory and digestive systems
- Connective tissue: sparsely located cells in a matrix secreted by those cells – functions in binding together and supporting other tissues, e.g. blood, cartilage, adipose, bone, tendons and ligaments
- Muscular tissue: long excitable cells (muscle fibre) capable of generating movement – functions in creating movement of limb and appendages (striated muscle) as well as in digestion (smooth muscle) and pumping blood around the body (cardiac and smooth muscle)
- Nervous tissue: excitable cells (called neurons) consisting of a cell body, dendrites and axons (which can be up to a metre long!) – functions in sensing stimuli and transmitting signals from one part of the body to the other
There are four main categories of plant tissue:
- Meristematic tissue: rapidly divides by mitosis to give rise to the other three types of plant tissue.
- Dermal tissue: covering layer of tissue – functions in protection.
- Vascular tissue: functions in transport of substances around the plant. There are two types of vascular tissue:
1. Xylem (transports water & minerals)
2. Phloem (transports glucose and amino acids)
- Ground tissue: makes up the bulk of plants and comprises the tissue between the dermis and vascular tissues – functions in photosynthesis, storage, and support.
Organ: group of tissues that carry out a particular function
- Examples of animal organs: heart; lungs; kidneys
- Examples of plant organs: leaf; flower; stem
Organ system: group of organs that carry out a number of linked functions
- Examples of animal organ systems: circulatory system
- Examples of plant organ system: root system
Tissue/Cell Culture: the growth of cells in a nutrient medium outside a living organism
Applications of tissue culture: It is possible to grow individual cells or groups of living cells (tissues) in artificial (in vitro), sterile growth medium, such as growing skin grafts. The growth medium contains a large mixture of many nutrients – including glucose, amino acids, hormones, minerals, vitamins, and antibiotics to prevent micro-organisms taking hold. Tissue culture is also used in cancer research and vaccine production and is artificial vegetative propagation of plants.