Science Biojournal- Entry 18

After researching a lot and sharing information with you all on food digestion, i hope everyone has learnt much more on this topic. And i now have a much clearer understanding of the digestion process . To wrap things up, i have a little video to share with everyone and i hope that you will like it!

If the video seems somewhat unclear, you can watch it from this link:http://www.youtube.com/watch?v=fff7xunqgtI

Science Biojournal- Entry 17

Stage 7 : Large Intestine

After the food has been passed through the small intestine, the food finally enters the large intestine, the final stage of digestion. The large intestine is roughly 1.5 meters long, with three parts: the cecum at the junction with the small intestine, the colon, and the rectum. The colon itself has four parts: the ascending colon, the transverse colon, the descending colon, and the sigmoid colon. The large intestine absorbs water from the bolus and stores feces until it can be egested.

Food products that cannot go through the villi, such as cellulose (dietary fiber), are mixed with other waste products from the body and become hard and concentrated feces. The feces is stored in the rectum for a certain period and then the stored feces is egested due to the contraction and relaxation through the anus. The exit of this waste material is regulated by the anal sphincter.

Science Biojournal- Entry 16

Stage 6: Small intestine

After being processed in the stomach, food is passed to the small intestine via the Pyloric sphincter. This is where the majority of digestion and absorption takes place as chyme enters the duodenum. Here it is further mixed with three different liquids:

1. bile, which emulsifies fats to allow absorption, neutralizes the chyme, and is used to excrete waste products such as bilin and bile acids (which has other uses as well). It is not an enzyme, however. The bile juice is stored in a small organ called the gall bladder.
2. pancreatic juice made by the pancreas.
3. intestinal enzymes of the alkaline mucosal membranes. The enzymes include: maltase, lactase and sucrase, to process sugars; trypsin and chymotrypsin are also added in the small intestine.

Most nutrient absorption takes place in the small intestine. As the acid level changes in the small intestines, more enzymes are activated to split apart the molecular structure of the various nutrients so they may be absorbed into the circulatory or lymphatic systems. Nutrients pass through the small intestine's wall, which contains small, finger-like structures called villi, each of which is covered with even smaller hair-like structures called microvilli. The blood, which has absorbed nutrients, is carried away from the small intestine via the hepatic portal vein and goes to the liver for filtering, removal of toxins, and nutrient processing.

The small intestine and remainder of the digestive tract then undergoes peristalsis to transport food from the stomach to the rectum and allow food to be mixed with the digestive juices and absorbed. The circular muscles and longitudinal muscles are antagonistic muscles, with one contracting as the other relaxes. As the circular muscles contract, the lumen becomes narrower and longer and the food is squeezed and pushed forward. When the longitudinal muscles contract, the circular muscles relax and the gut dilates to become wider and shorter to allow food to enter. In the stomach there is another phase that is called Mucus which promotes easy movement of food by wetting the food. It also nullifies the effect of HCl on the stomach by wetting the walls of the stomach as HCl has the capacity to digest the stomach.

Science Biojournal- Entry 15

Stage 4 : Stomach

At this stage of digestion, the food enters the stomach after passing through the cardiac orifice. In the stomach, food is further broken apart, and is later thoroughly mixed with a gastric acid and digestive enzymes that break down proteins. However the acid itself does not break down food molecules, rather, the acid provides an optimum pH for the reaction of the enzyme pepsin. The parietal cells of the stomach also secrete a glycoprotein called intrinsic factor which enables the absorption of vitamin B-12. Other small molecules such as alcohol are absorbed in the stomach as well by passing through the membrane of the stomach and entering the circulatory system directly.

Science Biojournal- Entry 14

Stage 3:Esophagus

At this point, the partially digested food enters the Esophagus, a narrow, muscular tube about 30 centimeters (12 inches) long, starts at the pharynx, passes through the larynx and diaphragm, and ends at the cardiac orifice of the stomach.

The wall of the Esophagus is made up of two layers of smooth muscles, which form a continuous layer from the Esophagus to the oten and contract slowly, over long periods of time. The inner layer of muscles is arranged circularly in a series of descending rings, while the outer layer is arranged longitudinally.

At the top of the Esophagus, is a flap of tissue called the epiglottis that closes during swallowing to prevent food from entering the trachea (windpipe). The chewed food is pushed down the Esophagus to the stomach through peristaltic contraction of these muscles. It takes only seconds for food to pass through the Esophagus, and little digestion actually takes place at this point!

Science Biojournal- Entry 13

Stage 2 : Oral cavity

Officially this is where digestion in human actually begins, in the oral cavity where food is chewed.

In the mouth, saliva is secreted in large amounts (1-1.5 litre/day) by three pairs of exocrine salivary glands in the oral cavity, which is then mixed with the chewed food by the tongue. There are two types of saliva. One is a thin, watery secretion, and its purpose is to wet the food. The other is a thick, mucous secretion, and it acts as a lubricant and causes food particles to stick together and form a bolus.

The saliva serves to clean the oral cavity and moisten the food, and contains digestive enzymes such as salivary amylase, which aids in the chemical breakdown of polysaccharides such as starch into disaccharides such as maltose. It also contains mucin, a glycoprotein which helps soften the food into a bolus.

The mechanism for swallowing is coordinated by the swallowing center in the medulla oblongata and pons. The reflex is initiated by touch receptors in the pharynx as the bolus of food is pushed to the back of the mouth.Swallowing transports the chewed food into the esophagus, passing through the oropharynx and hypopharynx.

Upon researching on this process, we have hereby learnt about the second process in food digestion

Science Biojournal- Entry 12

Stage one: Phases of Gastric Secretion
For this process, it can be divided into three phases: Cephalic phase, Gastric phase and intestinal phase.

First up is the Cephalic phase - This phase occurs before food enters the stomach and involves preparation of the body for eating and digestion. Sight and thought stimulate the cerebral cortex. Taste and smell stimulus is sent to the hypothalamus and medulla oblongata. After this it is routed through the vagus nerve and release of acetylcholine. Gastric secretion at this phase rises to 40% of maximum rate. Acidity in the stomach is not buffered by food at this point

The second phase is the Gastric phase - This phase takes 3 to 4 hours. It is stimulated by distention of the stomach, presence of food in stomach and increase in pH. Distention activates long and myentric reflexes. This activates the release of acetylcholine which stimulates the release of more gastric juices. As protein enters the stomach, it binds to hydrogen ions, which raises the pH of the stomach to around pH 6.

Finally, the Intestinal phase - This phase has 2 parts, the excitatory and the inhibitory. Partially-digested food fills the duodenum. This triggers intestinal gastrin to be released. Enterogastric reflex inhibits vagal nuclei, activating sympathetic fibers causing the pyloric sphincter to tighten to prevent more food from entering, and inhibits local reflexes.

Through these three phases of gastric secretion,it makes up the first part of food digestion.

Science Biojournal- Entry 11

For starters, i would like to explain what digestion is. Digestion is the breaking down of food in the body, into a form that can be absorbed and used or excreted. Also, it can be defined as the process by which the body breaks down food into smaller components that can be absorbed by the blood stream. And of course all takes place inside the digestive system! Now, the question is, what makes up of the digestive system? Well it actually starts with the phases of gastric secretion, moving on to the oral cavity, the Esophagus, the stomach and small intestine and finally the large intestine.

During the next few posts i will be going through the different phases of the digestion process

Science Biojournal-Entry 10

Hi there! In the previous few posts i have been researching on the topic: does age affect the quality of sperms. Now looking ahead, i will now be switching topics to digestion. Have you ever wondered what actually happens after you have placed food inside your mouth and how it travels into your body and most importantly, what happens to it? Well that is what we will be finding out in my next few posts!

Science Biojournal-Entry 9

I would like you to know that this would be my last entry on the topic issues on sex.

Throughout the course of researching on this topic,it is certainly uncommon to face some difficulties in obtaining information. However i believe that when there's a will, there's a way!



PS:Do note that i will be researching on another topic in the next entry.

Science Biojournal-Entry 8

Picking up from the previous post, we continue with a research showing that an interesting research study from the Netherlands showed that wearing tight leather trousers and tight plastic underwear together affected sperm motility, but neither had an effect alone.

Some evidence suggests that stress reduces semen quality, probably due to hormonal changes in the body that result from stress.

The causes of stress in modern life are legion and concerns over fertility or failure to conceive are very important causes of stress. If you are concerned that you have a fertility problem, it is sensible to seek advice from your family doctor.

The chance of conception in a healthy, young couple is about 20 per cent per month, so a delay of three to six months before conceiving is not unusual. It is reasonable to request an initial assessment after six months of regular unprotected intercourse without conception. So the main point i would like to bring across to everyone is to live a healthy lifestyle! :)

Science Biojournal-Entry 7

For todays post,now that we have found out on what causes men to lose fertility, the question is:How can I preserve my fertility?

Actually many factors are involve!
A few of the common factors are to:

• Adopt a healthy lifestyle, with a balanced diet and regular exercise.
• Don't smoke or use recreational drugs.
• Don't drink alcohol, or keep alcohol consumption within recommended limits.
• Try to avoid exposure to industrial and occupational hazards by following safety procedures and wearing protective clothing when provided.
• Avoid exposure to sexually transmitted diseases by adopting safer sexual practices, such as using condoms and reducing your number of partners.

Existing evidence does not suggest that wearing boxer shorts or immersing the testicles in cold water will improve semen quality. ( To be continued...)

Science Biojournal-Entry 6

In this entry, i would like to suggest to men on what caused the quality of their sperms deprove

Today, studies has shown that even environmental factors can affect male fertility! The factors include:
• endocrine disrupters
• toxic pollutants
• sexually transmitted infections
• zinc deficiency
• alcoholism
• smoking
• anabolic steroid use
• ionising radiation.

All this factors again reminds us of the importance of keeping the environment clean!

Adding to that, endocrine disrupters are chemicals present in the environment that, by virtue of their ability to adversely affect the endocrine (hormonal) system, can cause health consequences. Several industrial pollutants can affect fertility, as can smoking and alcohol use. Some of these toxins can cause reproductive disorders, neurological disease, immune system disorders and cancer!

Science Biojournal-Entry 5

After picking from the previous entry, we found out that unlike in women, the researchers found no correlation between male aging and chromosome changes that cause Down’s syndrome and other forms of trisomies – such as Klinefelter syndrome, Turner syndrome, triple X syndrome, and XYY in offspring – that are associated with varying types and severity of infertility as well as physical and neurological abnormalities. They did conclude, however, that some older men could be at risk for fathering children with dwarfism, and that “a small fraction of men are at increased risks for transmitting multiple genetic and chromosomal defects.”

In the case of Apert syndrome, a serious disfiguring birth defect, the researchers found that the effects of advancing male age may differ among different groups of men. Apert syndrome gene mutations increased in the sperm of a second group of men recruited in the Baltimore inner city by researchers at Johns Hopkins Medical Center, while no age effects were observed in the group of men recruited in California.

Wyrobek noted that these differences in finding suggest that factors other than age may be involved, raising the possibility that socioeconomic or dietary factors or ethnic background may also be involved in how age affects the quality of human sperm.

“Since some forms of genomic damage change with age and others don’t,” he said, “overall genomic sperm quality cannot be measured by any single sperm test.”

Science Biojournal-Entry 4

Does age affect the quality of the sperms?

The answer is : YES. There you have it! But why??


Actually studies has shown that genetic quality of sperm deteriorates as men get older,increasing a man’s risk of being infertile, fathering unsuccessful pregnancies and passing along dwarfism and possibly other genetic diseases to his children.

A study led by scientists at Lawrence Livermore National Laboratory (LLNL) and the University of California, Berkeley, found a steady increase in sperm DNA fragmentation with increasing age of the study participants, along with increases in a gene mutation that causes achondroplasia, or dwarfism. The first changes were observed in men in their early reproductive years.

Earlier research by the same team indicated that male reproductive ability gradually worsens with age, as sperm counts decline and the sperm lose motility and their ability to swim in a straight line.However, in the latest study, the researchers analyzed DNA damage, chromosomal abnormalities and gene mutations in semen samples from the same subjects – 97 healthy, non-smoking LLNL employees and retirees between 22 and 80 years old – and found that sperm motility showed a high correlation with DNA fragmentation, which is associated with increased risk of infertility and a reduced probability of fathering a successful pregnancy.( To be continued...)

Science Biojournal-Entry 3

For this third entry, i have decided to explain how sperms actually move about!

In evaluating motility with sperms, they are classified as non-motile, progressively motile or non-progressively motile. A progressively motile sperm swims forward in an essentially straight line, whereas a non-progressively motile sperm swims, but with an abnormal path, such as in tight circles.( An example could be seen in the picture above)

Another term that is sometimes used is "total motility" which refers to the fraction of sperm that display any type of movement. This concept is the norm for describing human sperm motility.

When analyzing motility, it is important to know whether the semen sample has been abused in any way. Exposure to heat, cold, any kind of residue on collection equipment, or the wrong pH or osmolality of an extender can adversely affect motility. Motility is also affected by periods of sexual inactivity - males that have not ejaculated for prolonged periods often have poor motility on the first ejaculate, but much better motility for a second ejaculate collected soon thereafter.

Science Biojournal-Entry 2

For this post, i think it would be appropriate to first give an explanation on what sperms are? During the past few days, i have found out that the word is actually derived from the Greek word sperma(meaning seed) and refers to the male reproductive cells.

It consists of a head, a midpiece and a tail. The head is the nucleus with densely coiled cromatinfibres, surrounded anteriorly by an acrosome( a cap-like structure that develops over the anterior half of the sperms head), which contains enzymes used for penetrating the female egg.

The midpiece has a central filamentous core with many mitochondria spiralled around it, used for ATP production for the journey through the female cervix, uterus and uterine tubes.

The tail or "flagellum" executes the lashing movements that propel the spermatocyte, and it consists of microtubules in an extension of the cell membrane.

Science Biojournal-Entry 1

My first topic i have chosen for bio journal is issues on sex. Interesting topic huh!
For starters the question i have chosen is something many people would be really interested to know: Does age affect the quality of the sperms? Therefore during the next few post i would be researching and finding out more on this area and hopefully by then i would be able to give you an answer!