Details In Human Body Structure System

Organelles

2011-12-04T17:44:00.000-08:00

The human body contains many different organs, such as the heart, lung, and kidney, with each organ performing a different function. Cells also have a set of "little organs", called organelles, that are adapted and/or specialized for carrying out one or more vital functions. Organelles are found only in eukaryotes and are always surrounded by a protective membrane. It is important to know some basic facts about the following organelles.

The Nucleus—A Cell's Center

The nucleus is the most conspicuous organelle found in a eukaryotic cell. It houses the cell's chromosomes and is the place where almost all DNA replication and RNA synthesis occur. The nucleus is spheroid in shape and separated from the cytoplasm by a membrane called the nuclear envelope. The nuclear envelope isolates and protects a cell's DNA from various molecules that could accidentally damage its structure or interfere with its processing. During processing, DNA is transcribed, or synthesized, into a special RNA, called mRNA. This mRNA is then transported out of the nucleus, where it is translated into a specific protein molecule. In prokaryotes, DNA processing takes place in the cytoplasm.

The Ribosome—The Protein Production Machine

Ribosomes are found in both prokaryotes and eukaryotes. The ribosome is a large complex composed of many molecules, including RNAs and proteins, and is responsible for processing the genetic instructions carried by an mRNA. The process of converting an mRNA's genetic code into the exact sequence of amino acids that make up a protein is called translation. Protein synthesis is extremely important to all cells, and therefore a large number of ribosomes—sometimes hundreds or even thousands—can be found throughout a cell.

Ribosomes float freely in the cytoplasm or sometimes bind to another organelle called the endoplasmic reticulum. Ribosomes are composed of one large and one small subunit, each having a different function during protein synthesis.

The Cytoskeleton—A Cell's Scaffold

2011-12-04T17:42:00.000-08:00

The cytoskeleton is an important, complex, and dynamic cell component. It acts to organize and maintain the cell's shape; anchors organelles in place; helps during endocytosis, the uptake of external materials by a cell; and moves parts of the cell in processes of growth and motility. There are a great number of proteins associated with the cytoskeleton, each controlling a cell’s structure by directing, bundling, and aligning filaments.

The Cytoplasm—A Cell's Inner Space

Inside the cell there is a large fluid-filled space called the cytoplasm, sometimes called the cytosol. In prokaryotes, this space is relatively free of compartments. In eukaryotes, the cytosol is the "soup" within which all of the cell's organelles reside. It is also the home of the cytoskeleton. The cytosol contains dissolved nutrients, helps break down waste products, and moves material around the cell through a process called cytoplasmic streaming. The nucleus often flows with the cytoplasm changing its shape as it moves. The cytoplasm also contains many salts and is an excellent conductor of electricity, creating the perfect environment for the mechanics of the cell. The function of the cytoplasm, and the organelles which reside in it, are critical for a cell's survival.

Genetic Material

Two different kinds of genetic material exist: deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). Most organisms are made of DNA, but a few viruses have RNA as their genetic material. The biological information contained in an organism is encoded in its DNA or RNA sequence.

Interestingly, as much as 98 percent of human DNA does not code for a specific product.

Prokaryotic genetic material is organized in a simple circular structure that rests in the cytoplasm. Eukaryotic genetic material is more complex and is divided into discrete units called genes. Human genetic material is made up of two distinct components: the nuclear genome and the mitochondrial genome. The nuclear genome is divided into 24 linear DNA molecules, each contained in a different chromosome. The mitochondrial genome is a circular DNA molecule separate from the nuclear DNA. Although the mitochondrial genome is very small, it codes for some very important proteins.

Cell Structures: The Basics

2011-11-27T18:24:00.000-08:00

The Plasma Membrane—A Cell's Protective Coat

The outer lining of a eukaryotic cell is called the plasma membrane. This membrane serves to separate and protect a cell from its surrounding environment and is made mostly from a double layer of proteins and lipids, fat-like molecules. Embedded within this membrane are a variety of other molecules that act as channels and pumps, moving different molecules into and out of the cell. A form of plasma membrane is also found in prokaryotes, but in this organism it is usually referred to as the cell membrane.

The Cytoskeleton—A Cell's Scaffold

The Cytoplasm—A Cell's Inner Space

Inside the cell there is a large fluid-filled space called the cytoplasm, sometimes called the cytosol. In prokaryotes, this space is relatively free of compartments. In eukaryotes, the cytosol is the "soup" within which all of the cell's organelles reside. It is also the home of the cytoskeleton. The cytosol contains dissolved nutrients, helps break down waste products, and moves material around the cell through a process called cytoplasmic streaming. The nucleus often flows with the cytoplasm changing its shape as it moves. The cytoplasm also contains many salts and is an excellent conductor of electricity, creating the perfect environment for the mechanics of the cell. The function of the cytoplasm, and the organelles which reside in it, are critical for a cell's survival.

Genetic Material

Interestingly, as much as 98 percent of human DNA does not code for a specific product.

Cell Organization

2011-11-27T18:15:00.000-08:00

Before we can discuss the various components of a cell, it is important to know what organism the cell comes from. There are two general categories of cells: prokaryotes and eukaryotes.

Prokaryotic Organisms

It appears that life arose on earth about 4 billion years ago. The simplest of cells, and the first types of cells to evolve, were prokaryotic cells—organisms that lack a nuclear membrane, the membrane that surrounds the nucleus of a cell. Bacteria are the best known and most studied form of prokaryotic organisms, although the recent discovery of a second group of prokaryotes, called archaea, has provided evidence of a third cellular domain of life and new insights into the origin of life itself.

Prokaryotes are unicellular organisms that do not develop or differentiate into multicellular forms. Some bacteria grow in filaments, or masses of cells, but each cell in the colony is identical and capable of independent existence. The cells may be adjacent to one another because they did not separate after cell division or because they remained enclosed in a common sheath or slime secreted by the cells. Typically though, there is no continuity or communication between the cells. Prokaryotes are capable of inhabiting almost every place on the earth, from the deep ocean, to the edges of hot springs, to just about every surface of our bodies.

Prokaryotes are distinguished from eukaryotes on the basis of nuclear organization, specifically their lack of a nuclear membrane. Prokaryotes also lack any of the intracellular organelles and structures that are characteristic of eukaryotic cells. Most of the functions of organelles, such as mitochondria, chloroplasts, and the Golgi apparatus, are taken over by the prokaryotic plasma membrane. Prokaryotic cells have three architectural regions: appendages called flagella and pili—proteins attached to the cell surface; a cell envelope consisting of a capsule, a cell wall, and a plasma membrane; and a cytoplasmic region that contains the cell genome (DNA) and ribosomes and various sorts of inclusions.

Eukaryotic Organisms

Eukaryotes include fungi, animals, and plants as well as some unicellular organisms. Eukaryotic cells are about 10 times the size of a prokaryote and can be as much as 1000 times greater in volume. The major and extremely significant difference between prokaryotes and eukaryotes is that eukaryotic cells contain membrane-bound compartments in which specific metabolic activities take place. Most important among these is the presence of a nucleus, a membrane-delineated compartment that houses the eukaryotic cell’s DNA. It is this nucleus that gives the eukaryote—literally, true nucleus—its name.

Eukaryotic organisms also have other specialized structures, called organelles, which are small structures within cells that perform dedicated functions. As the name implies, you can think of organelles as small organs. There are a dozen different types of organelles commonly found in eukaryotic cells. In this primer, we will focus our attention on only a handful of organelles and will examine these organelles with an eye to their role at a molecular level in the cell.

The origin of the eukaryotic cell was a milestone in the evolution of life. Although eukaryotes use the same genetic code and metabolic processes as prokaryotes, their higher level of organizational complexity has permitted the development of truly multicellular organisms. Without eukaryotes, the world would lack mammals, birds, fish, invertebrates, mushrooms, plants, and complex single-celled organisms.

This figure illustrates a typical human cell (eukaryote) and a typical bacterium (prokaryote). The drawing on the left highlights the internal structures of eukaryotic cells, including the nucleus (light blue), the nucleolus (intermediate blue), mitochondria (orange), and ribosomes (dark blue). The drawing on the right demonstrates how bacterial DNA is housed in a structure called the nucleoid (very light blue), as well as other structures normally found in a prokaryotic cell, including the cell membrane (black), the cell wall (intermediate blue), the capsule (orange), ribosomes (dark blue), and a flagellum (also black).

Cell Difination

2011-11-27T18:06:00.000-08:00

Cells are the structural and functional units of all living organisms. Some organisms, such as bacteria, are unicellular, consisting of a single cell. Other organisms, such as humans, are multicellular, or have many cells—an estimated 100,000,000,000,000 cells! Each cell is an amazing world unto itself: it can take in nutrients, convert these nutrients into energy, carry out specialized functions, and reproduce as necessary. Even more amazing is that each cell stores its own set of instructions for carrying out each of these activities.

The Immune System

2011-11-24T18:20:00.000-08:00

The immune system is one of nature's more fascinating inventions. With ease, it protects us against billions of bacteria, viruses, and other parasites. Most of us never reflect upon the fact that while we hang out with our friends, watch TV, or go to school, inside our bodies, our immune system is constantly on the alert, attacking at the first sign of an invasion by harmful organisms.

The immune system is very complex. It's made up of several types of cells and proteins that have different jobs to do in fighting foreign invaders. In this section, we'll take a look at the parts of the immune system in some detail. If you're reading about the immune system for the first time, we recommend that you take a look at the Immune System Overview first (see link below).

Human body part

2011-08-08T06:09:00.000-07:00

Short Note For Human Body

1. The human body is made up of a head, neck, torso, two arms and two legs. The average height of an adult human is about 5 to 6 feet tall. The human body is made to stand erect, walk on two feet, use the arms to carry and lift, and has opposable thumbs (able to grasp).

2. The adult body is made up of :100 trillion cells, 206 bones, 600, muscles, and 22 Internal organs.

3. There are many systems in the human body:

Circulatory System (heart, blood, vessels)
Respiratory System (nose, trachea, lungs)
Immune System (many types of protein, cells, organs, tissues)
Skeletal System (bones)
Excretory System (lungs, large intestine, kidneys)
Urinary System (bladder, kidneys)
Muscular System (Muscles)
Endocrine System (glands)
Digestive Systems (mouth, esophagus, stomach, intestines)
Nervous Systems (brain, spinal cord, nerves)
Reproductive System ( male and female reproductive organs)

4. Every square inch of the human body has about 19 million skincells.

5. Every hour about 1 billion cells in the human body must be replaced.

6. The average human head has about 100,000 hairs.

7. The circulatory system of arteries, veins, and capillaries is about 60,000 miles long.

8. The heart beats more than 2.5 billion times in an average lifetime.

9. There are about 9,000 taste buds on the surface of the tongue, in the throat, and on the roof of the mouth.

10. The strongest muscle in the body is the tongue.

11. The human heart creates enough pressure when it pumps out to the body to squirt blood 30 feet.

12. You blink over 10,000,000 times a year.

13. The human brain weight about 3 ponds.

14. it takes about 20 seconds for a red blood cell to circle the whole body.

15. Only 10% of the population are left handed.

16. One fourth of the bones in your body are in your feet.

17. Children tend to grow faster in the spring.

18. The most sensitive finger on the human hand is the index finger.

19. More men are color-blind than women.

20. More people have brown eyes than any other color.

Head

2011-08-08T05:44:00.000-07:00

Head

Forehead

2011-08-08T05:41:00.000-07:00

Forehead

Ear

2011-08-08T05:39:00.001-07:00

Ear

Eye

2011-08-08T05:38:00.000-07:00

Eye

Nose

2011-08-08T05:36:00.000-07:00

Nose

Cheek

2011-08-08T05:33:00.000-07:00

Cheek

Mouth

2011-08-08T05:28:00.000-07:00

Mouth

Chin

2011-08-08T05:27:00.000-07:00

Chin

Neck

2011-08-08T05:24:00.000-07:00

Neck

Adam's Apple

2011-08-08T05:20:00.000-07:00

Adam's Apple

Shoulder

2011-08-08T05:18:00.000-07:00

Shoulder

Arm

2011-08-08T05:16:00.000-07:00

Arm

Elbow

2011-08-08T05:12:00.001-07:00

Elbow

Forearn

2011-08-08T05:10:00.000-07:00

Forearn

Wrist

2011-08-08T05:08:00.000-07:00

Wrist

Hand

2011-08-08T05:04:00.000-07:00

Hand

Finger

2011-08-08T05:02:00.000-07:00

Finger

Chest

2011-08-08T05:00:00.000-07:00

Chest