Cause and Effect

Obesity

Obesity occurs when your body consumes more calories than it burns. In the past, many people thought that obesity was simply caused by overeating and under-exercising, resulting from a lack of will power and self-control. Although these are significant contributing factors, doctors recognize that obesity is a complex medical problem that involves genetic, environmental, behavioural, and social factors. All these factors play a role in determining a person's weight.

Recent research shows that in some cases, certain genetic factors may cause the changes in appetite and fat metabolism that lead to obesity. For a person who is genetically prone to weight gain (e.g., has a lower metabolism) and who leads an inactive and unhealthy lifestyle, the risk of becoming obese is high.

Although a person's genetic makeup may contribute to obesity, it's not the primary cause. Environmental and behavioural factors have a greater influence - consuming excess calories from high-fat foods and doing little or no daily physical activity over the long run will lead to weight gain. Psychological factors may also foster obesity. Low self-esteem, guilt, emotional stress, or trauma can lead to overeating as a means to cope with the problem.

Symptoms and Complications of Obesity

The health risks associated with obesity include:

ü  breathing disorders (e.g., sleep apnea, chronic obstructive pulmonary disease)

ü  certain types of cancers (e.g., prostate and bowel cancer in men, breast and uterine cancer in women)

ü  coronary artery (heart) disease

ü  depression

ü  diabetes

ü  gallbladder or liver disease

ü  gastroesophageal reflux disease (GERD)

ü  high blood pressure

ü  high cholesterol

ü  joint disease (e.g., osteoarthritis)

ü  stroke

People who are obese may have the symptoms of the medical conditions mentioned above. High blood pressure, high cholesterol levels, breathing problems, and joint pain (in the knees or lower back) are common. The more obese a person is, the more likely they are to have medical problems related to obesity.

Aside from the medical complications, obesity is also linked to psychosocial problems such as low self-esteem, discrimination, difficulty finding employment, and reduced quality of life.

Source:http://bodyandhealth.canada.com/channel_condition_info_details.asp?channel_id=1055&disease_id=95&relation_id=17519

Animals Classification

Animals

Among the most basic criteria by which animals are sorted is whether or not they possess a backbone. This single trait places an animal into one of just two groups: the vertebrates or the invertebrates and represents a fundamental division among all animals alive today as well as those that have long ago disappeared. If we are to know anything about an animal, we should first aim to determine whether it is an invertebrate or a vertebrate. We'll then be on our way to understanding its place within the animal world.

What are Vertebrates?

Vertebrates (Subphylum Vertebrata) are animals that possess an internal skeleton (endoskeleton) that includes a backbone made up of a column of vertebrae (Keeton, 1986:1150). The Subphylum Vertebrata is a group within the Phylum Chordata (commonly called the 'chordates') and as such inherits the characteristics of all chordates:

• bilateral symmetry
• body segmentation
• endoskeleton (bony or cartilaginous)
• pharyngeal pouches (present during some stage of development)
• complete digestive system
• ventral heart
• closed blood system
• tail (at some stage of development)

In addition to the traits listed above, vertebrates possess one additional trait that makes them unique among chordates: the presence of a backbone. There are a few groups of chordates that do not possess a backbone (these organisms are not vertebrates and are instead referred to as invertebrate chordates).

The animal classes that are vertebrates include:

• Jawless fish (Class Agnatha)
• Armored fish (Class Placodermi) - extinct
• Cartilaginous fish (Class Chondrichthyes)
• Bony fish (Class Osteichthyes)
• Amphibians (Class Amphibia)
• Reptiles (Class Reptilia)
• Birds (Class Aves)
• Mammals (Class Mammalia)

What are Invertebrates?

Invertebrates are a broad collection of animal groups (they do not belong to a single subphylum like the vertebrates) all of which lack a backbone. Some (not all) of the animal groups that are invertebrates include:

• Sponges (Phylum Porifera)
• Jellyfish, hydras, sea anemones, corals (Phylum Cnidaria)
• Comb jellies (Phylum Ctenophora)
• Flatworms (Phylum Platyhelminthes)
• Molluscs (Phylum Mollusca)
• Arthropods (Phylum Arthropoda)
• Segmented worms (Phylum Annelida)
• Echinoderms (Phylum Echinodermata)

Source: http://animals.about.com/od/zoologybasics/a/vertinvert.htm

The Digestive Process

The Digestive Process

The start of the process - the mouth: The digestive process begins in the mouth. Food is partly broken down by the process of chewing and by the chemical action of salivary enzymes (these enzymes are produced by the salivary glands and break down starches into smaller molecules).

On the way to the stomach: the esophagus - After being chewed and swallowed, the food enters the esophagus. The esophagus is a long tube that runs from the mouth to the stomach. It uses rhythmic, wave-like muscle movements (called peristalsis) to force food from the throat into the stomach. This muscle movement gives us the ability to eat or drink even when we're upside-down.
 
In the stomach - The stomach is a large, sack-like organ that churns the food and bathes it in a very strong acid (gastric acid). Food in the stomach that is partly digested and mixed with stomach acids is called chyme.
 
In the small intestine - After being in the stomach, food enters the duodenum, the first part of the small intestine. It then enters the jejunum and then the ileum (the final part of the small intestine). In the small intestine, bile (produced in the liver and stored in the gall bladder), pancreatic enzymes, and other digestive enzymes produced by the inner wall of the small intestine help in the breakdown of food.
 
In the large intestine - After passing through the small intestine, food passes into the large intestine. In the large intestine, some of the water and electrolytes (chemicals like sodium) are removed from the food. Many microbes (bacteria like Bacteroides, Lactobacillus acidophilus, Escherichia coli, and Klebsiella) in the large intestine help in the digestion process. The first part of the large intestine is called the cecum (the appendix is connected to the cecum). Food then travels upward in the ascending colon. The food travels across the abdomen in the transverse colon, goes back down the other side of the body in the descending colon, and then through the sigmoid colon.

The end of the process - Solid waste is then stored in the rectum until it is excreted via the anus.

Source: http://www.enchantedlearning.com/subjects/anatomy/digestive/

Definition The Human Heart

The Human Heart

The heart is one of the most important organs in the entire human body. It is really nothing more than a pump, composed of muscle which pumps blood throughout the body, beating approximately 72 times per minute of our lives. The heart pumps the blood, which carries all the vital materials which help our bodies function and removes the waste products that we do not need. For example, the brain requires oxygen and glucose, which, if not received continuously, will cause it to loose consciousness. Muscles need oxygen, glucose and amino acids, as well as the proper ratio of sodium, calcium and potassium salts in order to contract normally. The glands need sufficient supplies of raw materials from which to manufacture the specific secretions. If the heart ever ceases to pump blood the body begins to shut down and after a very short period of time will die.

The heart is essentially a muscle(a little larger than the fist). Like any other muscle in the human body, it contracts and expands. Unlike skeletal muscles, however, the heart works on the "All -or-Nothing Law". That is, each time the heart contracts it does so with all its force. In skeletal muscles, the principle of "gradation" is present. The pumping of the heart is called the Cardiac Cycle, which occurs about 72 times per minute. This means that each cycle lasts about eight-tenths of a second. During this cycle the entire heart actually rests for about four-tenths of a second.

Source: http://www.worldinvisible.com/apologet/humbody/heart.htm

Definition: The human heart

Glossary



Organ: a differentiated structure (as a heart, kidney, leaf, or stem) consisting of cells and tissues and performing some specific function in an organism.

Pump: a device that raises, transfers, delivers, or compresses fluids or that attenuates gases especially by suction or pressure or both.  

Muscle: a body tissue consisting of long cells that contract when stimulated and produce motion

Contracts: to reduce to smaller size by or as if by squeezing or forcing together.

Expands: to increase in extent or volume.

Skeletal muscles: striated muscle that is usually attached to the skeleton and is usually under voluntary control.
 

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