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| The Basic Body Plan |
THE BASIC BODY PLAN consists of cells, tissues, and organs. The cell is the basis of all life and they are constantly reproducing in our bodies to help us heal, grow, and biologically reproduce offspring. Tissues, like muscles, arteries, and skin, are all created from cells. More complex tissues, organized ones, form to make up the different organs in our bodies. All organs, work with other organs to function as organ systems, such as the reproductive system, the cardiovascular system, and the digestive system, just to name a few...
THE BASIC BODY PLAN: A CLOSER LOOK
Cells
Cells are the basis of all life. They are in charge of arranging molecules into living matter. ALL plants and animals have cells. Humans are believed to be carrying up to 100 trillion cells! Though we don't think about it, cells are constantly reproducing in our bodies to ward off uncalled for bacterias and virus, to replace dry skin, to grow hair, to produce blood, etc. Just about any task you can think of that occurs in the body, begins with a cell. Outside of these processes, cells are unique for they all contain the deoxyribonucleic acid (DNA) formula that contains our genetic information (see Lesson 2).
Two types of cells in the human body
1. Somatic Cells, the types of cells in our body that are used daily to help us heal, grow, and properly function.
2. Gametes, (sex cells), the types of cells that are found only in the reproductive system of the human body. Sperm cells (male), and egg cells (female).
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| Two types of cells in the human body |
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| The Cell Structure |
1. Plasma Membrane, A double-layered membrane, composed of phospholipids and protein molecules, that gives form to the cell and controls passage of material into and out of the cell.
2. Nucleus, Contains the genetic material (DNA), separated from the rest of the cell by a nuclear membrane.
3. Nucleolus, Seen as a dark mass in the nucleus, made up of proteins and ribosomal RNA, and the site of ribosome production.
4. Cytoplasm, Fluid, jelly-like substance, between the cell membrane and the nucleus, in which the organalles are suspended.
5. Mitochondria, Oblong organelle where adenosine triphosphate (ATP) production occurs; ATP is the carrier of chemical energy in the cell.
6. Ribosomes, Small structures made of proteins and RNA that "read" the RNA strand during protein synthesis; occur free and on endoplasmic reticulum.
7. Endoplasmic reticulum (e.r.), Membranous network of channels in cytoplasm, continous with nuclear membrane, that forms a pathway for transporting substances within the cell and stores synthesized molecules (intracellular circulatory system).
8. Centriole, Pairs of organelles composed of microtubules; organizes the cytoskeleton for cell division.
9. Lysosome, Sac-like attachment to cell membrane that digests unneeded molecules; formed from vesicles of Golgi body.
10. Golgi body and vesicle, Delivery system of cell, which collects, modifies, packages, and distributes vesicles, molecules that are synthesized at one location and used at another.
5. Mitochondria, Oblong organelle where adenosine triphosphate (ATP) production occurs; ATP is the carrier of chemical energy in the cell.
6. Ribosomes, Small structures made of proteins and RNA that "read" the RNA strand during protein synthesis; occur free and on endoplasmic reticulum.
7. Endoplasmic reticulum (e.r.), Membranous network of channels in cytoplasm, continous with nuclear membrane, that forms a pathway for transporting substances within the cell and stores synthesized molecules (intracellular circulatory system).
8. Centriole, Pairs of organelles composed of microtubules; organizes the cytoskeleton for cell division.
9. Lysosome, Sac-like attachment to cell membrane that digests unneeded molecules; formed from vesicles of Golgi body.
10. Golgi body and vesicle, Delivery system of cell, which collects, modifies, packages, and distributes vesicles, molecules that are synthesized at one location and used at another.
CHROMOSOMES (see also Lesson 3)
Most of the genetic information/material, deoxyribonucleic acid (DNA), that offspring inherit from their parents is located in the nucleus of cells. DNA is furthermore always packaged into chromosomes.
Chromosomes are visible only during cell division when they condense and contract. When cells are not dividing chromosomes remain uncoiled and defuse into a single-form called chromatin. When chromosomes are in their double state they comprise of an "arm," "centromere," and a "sister cromatid."
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| DNA is always packaged into chromosomes |
CHROMOSOMES IN HUMANS
In humans the number 46 refers to the amount of chromosomes that are found in somatic cells... 23 of these came from the male sperm, while the other 23 came from the female egg.
Diploid (46 chromosomes)
Haploid (23 chromosomes) contained within the gamete (egg or sperm)
When a haploid egg and sperm combine they form a fertilized egg called a zygote containing 46 chromosomes. The zygote quickly transforms/divides into a somatic cell (mitosis) and through a process called differentiation develops into three embryonic layers (endoderm, mesoderm, and ectoderm) that further devlelop into primitive organs, the skeletal system, the nervous system, and eyes. Human life begins!
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