Explain what is cell differentiation.
The process by which an unspecialised cell becomes specialised is called differentiation. All specialised cells e.g. liver cells, white blood cells, muscle cells, and originally came from stem cells. Stem cells are unspecialised cells, this means that they can develop into other types of cell. Stem cells divide by a process of mitosis (mitosis is cell division that produces genetically identical cells) to have new cells which then become specialised.
What two differences between embryonic and adult stem cells?
An adult stem cells are undifferentiated cells, which can be found throughout the body after the growth and development of the body.
The features of an adult stem cell are multiplying by the cell division to replace dying cells and regenerating damaged tissues. A main function of these cells is to maintain and repair the tissue in which they are found.
Embryonic stem cells are stem cells that are found in the embryo, the foetus or the blood within the umbilical cord at the early stage of development (at this stage the cell can transform into specialised cells and perform specific functions).
The features of embryonic cells are that they can differentiate into any cell type within the body. They also have the ability of unlimited self-renewal. This is not the case for the adult stem cells which have limited regeneration.
What does multipotent and totipotent stem cell mean?
Multipotent stem cells.
These cells have the same basic features of all stem cells. They are unspecialised cells that can self-renew for long time periods and differentiate into specialised cells, of closely related family of cells, with specific functions.
Most of the organs (e.g. brain, liver) contain multipotent stem cells, which provide the function to replace dead or damaged cells. REFER to figure A.
Totipotent stem cells
Totipotent cells can differentiate into all possible cell types. Such cells can construct a complete, usable organism. These cells are produced from the fusion of an egg and sperm cell. Cells are produced by the first few divisions of the fertilised egg. This is one of the most important stem cells because they can develop into any cell found in the body. REFER to figure A
The diagram below summaries the main differences:
For each tissue, explain what is the function of tissue and give at least three features of the cells of each tissue explaining how each feature is related to the function.
Connective tissue, is a tissue that connects, supports, combines and separates other tissues or organs. Connective tissue mainly consists of collagen, elastic fibres, fatty tissue, cartilage or bone. This tissue can be found throughout the body.
The function of connective tissue is to transport fluids and dissolved materials, protecting organs, supporting and moving joints and defending the body from microorganisms.
Blood is a type of connective tissue. The main functions of blood are transportation, protection and regulation.
Features of the blood include disc-shaped cells, with a dent on each side, this creates a large surface area for gas exchange. It contains haemoglobin (a special pigment that combines with oxygen). It has no nucleus, meaning there are more space for oxygen and haemoglobin. REFER to figure B
Epithelial is a tissue Is a type of tissue that, lines the body’s cavities and organs.
The functions of epithelial tissue include, a physical protection (meaning protection from abrasion, dehydration and from destruction by chemical or biological agent). Control of permeability (what can enter and leave the cell). Secretion (production of digestive juice, hormones and sweat).
Simple Squamous epithelium is a type of epithelial tissue. These tissues provide a function that allows the passage of materials by diffusion and filtration.
The features of simple squamous epithelium include tightly packed cells, a single thin layer Figure x below. (not very good for protection). The tissue also provides the function of control diffusion, osmosis and filtration processes. REFER to figure C
Muscle tissue is a bundle of fibrous tissue that can contract and producing movement and keeping the position of parts in the body.
The functions of muscle tissue are creating motion, meaning muscles work with nerves, bones and joints to produce body movements. Stabilize body position and maintain posture.
Skeletal muscle is the type of muscle cell. Skeletal muscle is under control of the somatic nervous system (voluntary control). The function of skeletal muscle is to produce movement, maintain posture and generate heat.
Features of skeletal muscle include the ability of the muscle tissue to lengthen when contracting and producing movement. It is also elastic allowing the muscle tissue to return to its normal length after its been stretched. It also features contractility, providing the muscle with the ability of muscle self-contraction.
Nervous tissue is a cable-like bundle of parallel axons.
Nervous tissue is found within the bodies nervous system and is made up of unique and specialised cells. Like an electrical circuit the nervous system transmits signals to the spinal cord and brain. The neuron cells receive/conduct these signals allowing the body to use its senses.
Nerve cells are a type of nervous tissue. The function of nerve cell is to carry messages called impulses from one part of the body to another.
The features of nerve cell are that they have extremely elongated (long) cells allowing the nerves spread around the body. Nerve cell has many branches at both ends to connect to other nerve cells. Nerve cell has cell body which contains organelles and it plays critical role in integrating stimuli from other neurons. The diagram below, Figure D, shows a simple diagram of the nerve tissue
Compare different tissues with similar functions. Make 5 comparisons, including both similarities and differences between the tissues and describe the role of the features you have described.
A comparison of the Cardiac, smooth and skeletal muscles
Muscle tissue is made up of excitable cells that are long and fibrous. These cells are ready for contraction, or the activation of tension in our muscles, making it possible for us to move our body parts. They are arranged in parallel lines and are bundled, making muscle tissue very strong. REFER to figure E
Skeletal Muscle movements are voluntary, because we have direct control over them through nervous impulses from our brains sending messages to the muscle. The cells are striated with the striations perpendicular to the muscle fibres and it is mainly found attached to bones.
The Cardiac Muscles movements are involuntary, due to our inability to control its movements, the cells are striated, and branched with intercalated discs.
Smooth Muscle movements are involuntary, the cells are non-striated, and spindle shaped and is found in blood vessels.
The three tissues have a similarity’s, an example is the carbon dioxide and oxygen gas are involved contraction of these tissues (oxygen is exchanged with carbon dioxide in the blood during aerobic respiration). These tissues have actin and myosin filaments involved in their functions (actin and myosin are responsible for the cell movements, myosin is type of motor i.e. protein that uses the stored energy as ATP, for movement for a specific function).
Smooth and cardiac muscles are involuntary compared to skeletal muscle this means the muscles are not under your conscience control).
Skeletal and smooth muscles have the ability of regeneration (muscle fibres can lay down new protein and enlarge, regenerating the damaged muscle tissue)
Cardiac cells fit together tightly at dark-staining junction called intercalated discs (the role of intercalated disc to connect muscle cells together)
The Cardiac muscle also shares many properties with smooth muscle, including control by the autonomic nervous system and spontaneous (automatic) contractions.
Cardiac and skeletal muscles are similar in that both appear to be “striated” in that they contain sarcomeres.