Specialized Cells & Tissues Biology Lesson # 4 Specialized Cells & Tissues

Specialized Cells All cells come from pre-existing cells (cell theory), and all cells begin as a single cell (a zygote); this zygote then begins to divide and cells develop in different ways. We are multicellular organisms – made up of trillions of cells. Not all of the cells are exactly the same – they do all have the same DNA information, but they all do specialized jobs. Cells develop in different ways to perform particular functions in a process called cell specialization. For example, animal cells may become specialized to form skin cells, or brain cells, and animal cells can specialize to form root cells, stem cells, etc.

Regeneration Regeneration is the process whereby a body part is replaced or regrown. The best example of regeneration is the salamander – it can regrow amputated limbs, tails, eye lenses, and even some parts of its heart! This is very unique, and regeneration is rare in humans. There are a few special cases, but only the liver is known to naturally regenerate. There have been cases where children’s fingertips have regrown if amputated. There have also been cases where limbs where regenerated in the lab, such as a functioning bladder.

Stem Cells Unspecialized cells in the body are called stem cells – this is the very first cell we came from. Stem cells specialize when exposed to proper environmental conditions, or sometimes they stay unspecialized and simply go through the phases of the cell cycle. Scientists believe that stem cells may be used to treat injury or disease by regenerating organs, since they are able to become any cell in the human body.

2 Types of Stem Cells Embryonic stem cells – found in embryos, and are able to undergo differentiation, which is the first step in specialization – they start to look differently and perform different functions, until the divide enough and specialized further, when they become adult stem cells. Adult stem cells – the cells are now left with a limited ability to create a variety of cells types. There are some adult stem cells found in skin, blood, and neural tissue, but not many.

Stem Cells (continued) Since embryonic stem cells are much more useful in becoming specific specialized cells for damaged tissues, there is an ethical debate that has arisen. Small amounts of these cells can be taken from the umbilical cord or placenta shortly after birth, and stored for possible later use, like for the treatment of leukemia. The embryo must be destroyed in order to collect a large amount of its stem cells. The Catholic Church is opposed to any action that destroys human life.

Videos Stem Cell Basics Stem Cell Research – Adult & Embryonic (first 5-6 minutes only)

Animal Tissues Specialized cells group together to perform their tasks, and these groups of cells are called tissues. There are four types of tissues in animals.

Epithelial Tissue Cells tightly packed together to form a protective barrier. Can be one cell thick or several layers of cells. Lines body cavities and surfaces, protects structures, and forms glands that produce hormones, enzymes, and sweat.

Connective Tissue Cells used to join other tissues together and forms blood, stores fat, fills empty space tendons (connecting muscle to bone) ligaments (bones to bones) cartilage blood

Muscle Tissue Three types that allow for movement including skeletal (moving limbs – voluntary movement) smooth (blood vessels and organs – involuntary movement) cardiac (the heart – involuntary movement)

Nervous Tissue Nerve cells which create messages within the body, called impulses, and transmit them throughout the body. Nerve cells can also receive messages from outside the body

Blood Made up of plasma, red blood cells, white blood cells, and platelets. Plasma is the aqueous part of blood, and contains many nutrients. Red blood cells contain haemoglobin, a protein that can absorb and release oxygen. White blood cells protect the body from bacteria and viruses, and fight infection Platelets are cells that help in the process of blood clotting

Videos Animal Tissues Blood