There are few millions to billions of cells in an animal body based on its weight and size.
Animal cells are quite unique than the plant cells in many aspects.
Unlike in plants, there are different types of cells with diverse functions.
They vary based on the body organ and type of tissue they form.
Animal Cell Facts
1. Lack of nucleus: Animal cells are eukaryotic and have a prominent nucleus. But, not all cells have the nucleus in them. For examples, the red blood cells have no nucleus. Hence, they are called red blood corpuscles instead of cells. They are formed from the bone marrow tissue. These RBC cells do not need a nucleus as they are not going to multiply by mitosis or meiosis. Also, the hemoglobin inside them occupies most of the space.
2. Totipotency: This is an ability of the the cells to convert into any other required cell in the body. Stem cells are the ones which are totipotent. They can be found in dental growth tissue, placenta, umbilical cord blood of newborn babies. In the body, these stem cells convert into cells as per the organ needs. Thus, they help to repair a damaged tissue or replace a worn out tissue.
3. Ability to swim: Some animal cells can swim when required. Protozoans are examples of the cell which can swim. Besides male gamete containing sperm cells are also able to swim towards the ova in the uterus. They have a tail which enables them to swim and reach to ova to fertilize.
4. Receptors: Most cells have plasma or cell membranes which have receptors. Receptors are the protein structures which receive a signal from external agents and pass it in to the cell. This is the way the drugs we take act at the cellular level and bring the required effects. There are four types of receptors with diverse functions.
5. Telomer decides lifespan: Cells divide by mitosis and multiply in numbers. For each cell division, the telomere length goes down and it decides the lifespan of a cell. Cell life also depends on the stress, health, nutrition and other conditions. As per Hayflick limit, a cell has the capacity to undergoes approximately 40 to 60 divisions by mitosis. Then after, it goes for senescence phase and die by programmed cell death.
6. Self-repair: During the process of physiology and daily life activities, the cell tends to have some malfunctions. This happens in terms of abnormalities in DNA strand, RNA strand, protein arrangement, etc. But, of them DNA repair is crucial and happens almost every day. The cells immediately correct the malfunction for their stability. If unable to correct, they go for self destruction.
7. Self-destruction: As mentioned before, cells can trigger death on to themselves. When there is an injury to the cells or a faulty DNA is formed, they go for self-destruction to avoid damage to other cells. This self-destruction occurs by a process called as apoptosis.
8. Lack of multiplication and division: Animals cells undergo either mitosis or meiosis to multiply their numbers. But nerve cells are an exception. They never divide or multiply once formed during birth. There is damage; they try to innervate the surrounding area by plasticity.
9. Chemotaxis activity: This a mechanism wherein cells move towards one part of the body due to chemical guidance. This is seen in white blood cells. When there is an infection or wound in one part of the body, the WBC cells migrate to that point for defense and repair. Hence you will notice pus in the area of wounds, infection or even cancer. The intention of migration is to
10. Cell eating: Cells can eat by themselves. Macrophages and neutrophils are the type of white blood cells which engulf any harmful bacteria or toxins in the body. This cell eating is called as phagocytosis. Neutrophils eat any harmful bacteria present in the blood circulation. While, the macrophages engulf any pathogenic microbes in the tissues.
11. Cell drinking: Cell can also drink liquid material or substances by a process known as pinocytosis. This seen mostly in protozoa like the amoeba.
12. Cell content: Almost 70% of cell matter is made of water, the remaining portion is made of proteins, carbohydrates, lipids, micro-elements, etc.
13 Vision: Cells like rods and cones in the eye make it possible to view light and color. Cats have six to eight times more rods. Due to this, they can see in the dark at night. Insects have compound eyes and they have multiple visions. So, a single object appears as multiple objects to them.
14. Organelle location: The location or organelles varies based on the requirement of other factors. In nerve cells, the mitochondria are concentrated at the nerve endings to generate the energy required for signal transduction.