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Designer: Lisee
Copyrighted 2007 Nicolette.

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3:40 AM

time flies. and now, this will be my last entry for the Biology Journal project. i can say that it has been a pleasant and enriching experience to learn biology in this way. and the fact is that, i have learnt a great deal on the 2 topics that i have researched on- digestion and transport in living things.

although it has been strenuous for me, trying to keep up with the constant updates of my entries, i found out that i can learn a lot more just by researching on the topics that i chose and locating key words or important details from the chunk of information i received.

i admit it was not an easy task to make a good entry, but at least i tried my best to do the best out of it. and although this will be my last post, the knowledge that i have learnt through everything i have done will always remain as mine.

8:11 AM

After learning such a great deal about the transport system in plants, let me add on to some other findings on xylem and phloem tubes:

xylem:

• made of dead cells
• thick cell walls
• cell walls made of lignin (a hard cellulose-like substance which gives rigidity to plant tissues)
• impermeable
• cross walls absent
• no cytoplasm
• transport of water and minerals
• carried to leaves
• upward flow
• tissue has fibres

phloem:

• made of living cells
• thin cell walls
• cell walls made of cellulose
• permeable
• has perforated cross walls called sieve plates
• cells lined with cytoplasm strands
• transport of food
• carried to growing parts and storage organs
• upward and downward flow
• tissue has companion cells

Ok, this marks the end of my biology journal. i hope that all of you will take away some valuable knowledge with you after reading my entries. thank you(:

7:15 AM

6:30 AM

Xylem vessels are like long drainpipes reaching all the way from the roots to the tip of every leaf. They are made up of hollow dead cells joined end to end.

Water and dissolved mineral salts are drawn up the xylem vessels when water from the leaves evaporates and diffuses out through tiny holes called stmata into the air. This process whereby plants lose water due to evaporation is called transpiration. As transpiration continues, more water is pulled up the xylem as though someone is "sucking" water up the plant. The movement of water with dissolved mineral salts through the plants is called the transpirational pull. Other phenomena that cause xylem sap to flow are the following- cohesion and adhesion & root pressure.

Transpirational pull- As water evaporates from the leaves of the plant,there is a suction created by this action resulting in a pull drom the roots..

Cohesion and Adhesion- The water molecules are cohesed(attracted) to each other forming a continuous column of water. They also are adhesed(attracted) to the xylem vessel(a thin tube) in the plant.

Root pressure- The water molecules surounding the root are very much eager to enter the root(due to less water potential in the root).Thus the root exerts a pressure towards the water in the xylem vessel.


the transpirational pull

image courtesy of:
www.progressivegardens.com/.../transpiration.jpg

4:00 AM

Today, we will start off with the roots of a plant. Plants usually obtain their water and dissolved minerals from the soil through their root hairs near the tip of each root. Water moves into the root hairs near the tip of each root. Water moves into the root hairs by osmosis.

Osmosis is the process by which water molecules move from the soil with a high concentration of water molecules into the root hair cell with a lower concentration of water molecules through the partially permeable cell membrane.



Dissolved mineral salts are absorbed into the root hairs by diffusion or active transport. When the concentrarion of mineral salts in the soil water water is higher than in the root hairs,the mineral salts diffuse into the cells of the root hairs.

When the concentration of mineral salts in the soil water is lower than in the root hairs, the mineral salts are absorbed into the cells of the root hairs by active transport. Active transport is a process that uses energy from the respiration of a plant.

Through the process of osmosis, diffusion and active transport, the water and dissolved mineral salts in the roots move from cell to cell towards the xylem vessels that carry them up the plant.

8:57 PM

We have learnt that the 3 main components of human circulatory system are the heart, blood vessels and blood respectively. I'm sure all of us would have a substantial amount of knowledge about them. And now, let's continue finding out more information about the transport system in plants!

Now, let me give all of you a brief overview of the plant's transport system.



Plants have a transport system too, in some ways similar to an animal's blood circulatory system. However, there is still a number of differences between the two. For example, there isn't a part in the plant's transport system that acts like the human heart, which pumps blood around the entire body. There isn't any circulating cells present, and also liquid do not move around continuously in plants.

The substances which are transported are- water and mineral salts, such as calcuim ions, magnesium ions, nitrate ions and phosphate ions from the soil and glucose from the leaves after photosynthesis.

In the next few posts, we will dicuss on the components that that makes up the plant's transport system, which extends from the roots, up through the stems to the leaves, flowers and fruits.

image courtesy of:
http://www.uic.edu/classes/bios/bios100/lectf03am/lect18.htm

7:51 PM

White Blood Cells














image of a single human lymphocyte

6:27 AM

I've completed the two main components of human transport system, which are the heart and blood vessels. Hence, i will now advance to the third component- blood.

Do you ever wonder what makes up blood? Unless you need to have blood drawn, donate it or have to stop its flow after an injury, you probably don't think much about it. But blood is the most commonly tested part of the body, and it is truly the river of life. Every cell in the body gets its nutrients from blood.

Blood is a mixture of two components: cells and plasma. The heart pumps blood through the arteries, capillaries and veins to provide oxygen and nutrients to every cell of the body. The blood also carries away waste products. The adult human body contains approximately 5 litres of blood and it makes up 7 to 8 percent of a person's body weight.

Plasma is the liquid portion of the blood. Blood cells like red blood cells float in the plasma. Also dissolved in plasma are electrolytes, nutrients and vitamins (absorbed from the intestines or produced by the body), hormones, clotting factors, and proteins such as albumin and immunoglobulins (antibodies to fight infection). Plasma distributes the substances it contains as it circulates throughout the body.

The cellular portion of blood contains red blood cells, white blood cells and platelets.


Red Blood Cells

Red blood cells perform the most important blood duty. A single drop of blood contains millions of red blood cells which are constantly traveling through your body delivering oxygen and removing waste. If they weren't, our body would slowly die.




Microscopic image of red blood cells

Red blood cells are red only because they contain a protein chemical called hemoglobin which is bright red in color. Hemoglobin contains the element Iron, making it an excellent vehicle for transporting oxygen and carbon dioxide. As blood passes through the lungs, oxygen molecules attach to the hemoglobin. As the blood passes through the body's tissue, the hemoglobin releases the oxygen to the cells. The empty hemoglobin molecules then bond with the tissue's carbon dioxide or other waste gases, transporting it away.


Hemoglobin

Over time, the red blood cells get worn out and eventually die. The average life cycle of a red blood cell is 120 days. Your bones are continually producing new blood cells, replenishing your supply. The blood itself, however, is re-circulated throughout your body, not being remade all of the time.

Since the human body is continually making more blood, it is safe for healthy adults to donate blood. The blood is then stored for use in emergency situations. Initially after giving blood, the donor may feel some momentary lightheadedness due to the loss of oxygen-rich red blood cells and blood sugar. The body quickly stabilizes itself.

Reference:
http://health.howstuffworks.com/blood.htm
http://en.wikipedia.org/wiki/Blood

Photo courtesy:
Garrigan.Net

3:42 AM

today, i will move on to the second main component of the human circulatory system- blood vessels. Blood vessels are part of the circulatory system and function to transport blood throughout the body.

There are 4 types of blood vessels.

1. Arteries
Arteries are elastic vessels that transport blood away from the heart. The largest artery of the body is the aorta. The aorta originates from the heart and branches out into smaller arteries. The smallest arteries are called arterioles which branch into capillaries.



2. Veins
Veins are elastic vessels that transport blood to the heart. The smallest veins in the body are called venules. They receive blood from the arteries via the arterioles and capillaries. The venules branch into larger veins which eventually carry the blood to the largest veins in the body, the vena cava. The blood is then transported from the vena cava to the right atrium of the heart. The size of a vein is around 1 millimeter to 1-1.5 centimeters in diameter.



The artery and vein wall consists of three layers:

- tunica adventitia
The tunica adventitia is the strong outer covering of arteries and veins. It is composed of connective tissue as well as collagen and elastic fibers. These fibers allow the arteries and veins to stretch to prevent overexpansion due to the pressure that is exerted on the walls by blood flow.

- tunica media
The tunica media is the middle layer of the walls of arteries and veins. It is composed of smooth muscle and elastic fibers. This layer is thicker in arteries than in veins.

- tunica intima
The tunica intima is the inner layer of arteries and veins. In arteries this layer is composed of an elastic membrane lining and smooth endothelium that is covered by elastic tissues. Veins do not contain the elastic membrane lining that is found in arteries. In some veins the tunica intima layer also contains valves.



3. Capillaries
Capillaries are extremely small vessels located within the tissues of the body that transport blood from the arteries to the veins. Capillary walls are thin and are composed of endothelium (a single layer of overlapping flat cells). Oxygen, carbon dioxide, nutrients and wastes are exchanged through the thin walls of the capillaries.

The flow of blood is controlled by structures called precapillary sphincters. These structures are located between arterioles and capillaries and contain muscle fibers that allow them to contract. When the sphincters are open, blood flows freely to the capillary beds of body tissue. When the sphincters are closed, blood is not allowed to flow through the capillary beds.

Capillaries are so small that red blood cells can only travel through them in single file.
- 5-10 microns in diameter.



4. Sinusoids
The liver, spleen and bone marrow contain vessel structures called sinusoids instead of capillaries. Similar to capillaries sinusoids are composed of endothelium. The individual endothelial cells however do not overlap as in capillaries and are spread out. Oxygen, carbon dioxide, nutrients, proteins and wastes are exchanged through the thin walls of the sinusoids. The size of a sinusoid is around 30-40 microns in diameter.


additional information:

Microcirculation deals with the flow of blood from arterioles to capillaries or sinusoids to venules. Blood flows freely between an arteriole and a venule through a vessel channel called a thoroughfare channel. Capillaries extend from this channel and structures called precapillary sphincters control the flow of blood between the arteriole and capillaries.

The precapillary sphincters contain muscle fibers that allow them to contract. When the sphincters are open, blood flows freely to the capillary beds where gases and waste can be exchanged with body tissue. When the sphincters are closed, blood is not allowed to flow through the capillary beds and must flow directly from the arteriole to the venule through the thoroughfare channel.

It is important to note that blood is supplied to all parts of the body at all times but all capillary beds do not contain blood at all times. Blood is diverted to the parts of the body that need it most at a particular time. For instance when you eat a meal blood is diverted from other parts of your body to the digestive tract.

Vessel Sizes (Diameter in Microns)

Arterioles
20-50

Capillaries
5-10

Sinusoids
30-40

Venules
30-40

Images courtesy of:
MedValet
Carolina Biological Supply/Access Excellence

3:55 AM

In this post, the main focus will be on one of the main components of the circulatory system- the heart. Let's take a look on the anatomy of the human heart.

The heart sends blood around our body. The blood provides our body with the oxygen and nutrients it needs. It also carries away waste. Our heart is sort of like a pump, or two pumps in one. The right side of your heart receives blood from the body and pumps it to the lungs.





Heart Parts

The heart is made up of four different blood-filled areas, and each of these areas is called a chamber. There are two chambers on each side of the heart. One chamber is on the top and one chamber is on the bottom. The two chambers on top are called the atria. (singular: atrium) The atria are the chambers that are filled with blood returning to the heart from the body and lungs. The heart has a left atrium and a right atrium.

The two chambers on the bottom are called the ventricles. The heart has a left ventricle and a right ventricle. Their job is to squirt out blood to the body and lungs. Running down the middle of the heart is a thick wall of muscle called the septum. The septum's job is to separate the left side and the right side of the heart.

The atria and ventricles work as a team— the right atrium pumps the blood to the right ventricle, which then pumps the blood to the lungs via the pulmonary artery. After passing through the richly vascularized lung tissue, oxygen-rich blood return to the heart via the pulmonary vein and into the left atrium. The left atrium pumps the blood to the left ventricle, the launching pad that pumps the blood through the huge aortic artery and delivers blood to the rest of the body.

Well, our blood relies on four special valves inside the heart. A valve maintains the unidirectional flow of blood by opening and closing depending on the difference in pressure on each side. It keeps the flow of blood there by closing.

Two of the heart valves are the mitral valve and the tricuspid valve. They let blood flow from the atria to the ventricles. The other two are called the aortic valve and pulmonary valve, and they're in charge of controlling the flow as the blood leaves the heart. These valves all work to keep the blood flowing forward. They open up to let the blood move ahead, then they close quickly to keep the blood from flowing backward.


reference:
http://www.wanderings.net/
http://en.wikipedia.org/wiki/Heart_valve

6:51 AM

moving on from digestion, we will now move on to the next topic: transport in living thing. i am going to come up with one question to research on: what are the differences between the components of the transport system in humans and plants?

firstly, i will start off with human transport system. here is the main overview.

The circulatory system is an organ system that moves nutrients, gases, and wastes to and from cells, helps fight diseases and helps stabilize body temperature and pH to maintain homeostasis. The main components of the human circulatory system are the heart, the blood, and the blood vessels. The circulatory system includes: the pulmonary circulation and the systemic circulation.


the human circulatory system
red indicates oxygenated blood
blue indicates deoxygenated blood


additional information:

pH: pH is the measure of the acidity or alkalinity of a solution.

Homeostasis: the property of either an open system or a closed system, especially a living organism, that regulates its internal environment so as to maintain a stable, constant condition.


you may not be able to understand some of the terms used here. but don't worry. in the next post, i will give you a more detailed explanation on each and every one of them(:


reference:
http://en.wikipedia.org/wiki/Homeostasis
http://en.wikipedia.org/wiki/PH

5:43 AM

once food has passed through the small intestine, it is mostly undigestible material and water. it enters the large intestine, named for its wide diameter. the large intestine has six parts: the cecum, ascending colon, transverse colon, descending colon, sigmoid colon, and rectum.

the most common explanation is that the appendix is a vestigial structure with no absolute purpose. in The Story of Evolution, Joseph McCabe once argued:

the vermiform appendage—in which some recent medical writers have vainly endeavoured to find a utility—is the shrunken remainder of a large and normal intestine of a remote ancestor. this interpretation of it would stand even if it were found to have a certain use in the human body. vestigial organs are sometimes pressed into a secondary use when their original function has been lost.

given the appendix's propensity to cause death via infection, and the seemingly perfect health of those who have had their appendix removed, the biological purpose of the appendix has mystified scientists for some time. there have been cases of people who have been found, to have a congenital absence of an appendix. there have been no reports of impaired immune or gastrointestinal function in these people.


defecation is the final act of digestion by which organisms eliminate solid, semisolid or liquid waste material from the digestive tract via the anus. when humans expel feaces, waves of muscular contraction known as peristalsis in the walls of the colon move fecal matter through the digestive tract towards the rectum. undigested food may also be expelled this way. this process is called egestion.

information is taken from:
http://en.wikipedia.org/wiki/Vermiform_appendix
http://en.wikipedia.org/wiki/Defecation

6:08 AM

now, i will continue from the previous post.

1:20 AM

The small intestine is about 20 feet (6 meters) long and has three parts: the duodenum, jejunum, and ileum. The duodenum is where most chemical digestion takes place. Here, bile from the gallbladder and enzymes from the pancreas and intestinal walls combine with the chyme to begin the final part of digestion.

Bile liquid is created in the liver and stored in the gallbladder. Bile emulsifies (breaks into small particles) lipids (fats), which helps in the mechanical digestion of fats. The pancreas and gland cells of the small intestine secrete digestive enzymes that chemically break down complex food molecules into simpler ones. These enzymes include trypsin (for protein digestion), amylase (for carbohydrate digestion), and lipase (for lipid digestion).

When food passes through the duodenum, digestion is complete.



in the next post, i will move on to the digestion in jejunum and ileum.

9:43 PM

In the stomach, food undergoes chemical and mechanical digestion. Here, peristaltic contractions (mechanical digestion) churn the bolus, which mixes with strong digestive juices that the stomach lining cells secrete (chemical digestion).

8:23 PM

after the swallowing of the food, the next stop in the digestive system is the Esophagus, also known as the gullet.

the esophagus, a narrow, muscular tube about 30 centimeters 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. 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.

9:23 PM

the first stage of digestion begins in the mouth, where our teeth grind and chew food, breaking it into small manageable pieces. this chewing process, known as mastication, is dependent upon powerful muscles (masseter and temporalis), as well as smaller muscles that permit fine control. they move the lower jawbone against the upper jaw, enabling the crushing of hard food.

mastication causes exocrine glands under the tongue and in the back of the mouth to secrete a watery liquid called saliva which performs two essential functions:

1. it moistens and compacts the chewed food so the tongue can roll it into a ball (bolus) and push it to the back of your mouth for swallowing and easy passage through the pharynx and
esophagus.

2. saliva contains digestive enzymes which begin the breakdown of carbohydrates.

mastication and saliva secretion work in harmony, as chewing increases the surface area of food which helps to accelerate the breakdown of starch molecules into simple sugars by the digestive enzymes.


more facts about the salivary gland:

Salivary glands:
#1 is Parotid gland,
#2 is Submandibular gland,
#3 is Sublingual gland

the parotid glands are a pair of glands located in the subcutaneous tissues of the face overlying the mandibular ramus and anterior and inferior to the external ear. the secretion produced by the parotid glands is serous in nature, and enters the oral cavity through the Stensen's duct. despite being the largest pair of glands, only approximately 25% of saliva is produced by the glands.

the submandibular glands are a pair of glands located beneath the floor of the mouth, superior to the digastric muscles. the secretion produced is a mixture of both serous and mucous and enters the oral cavity via Wharton's ducts. approximately 70% of saliva in the oral cavity is produced by the submandibular glands.

the sublingual glands are a pair of glands located beneath the floor of the mouth anterior to the submandibular glands. the secretion produced is mainly mucous in nature, however it is categorized as a mixed gland. approximately 5% of saliva entering the oral cavity come from these glands.

information is taken from:
http://en.wikipedia.org/wiki/Salivary_gland

6:50 AM

to start off with the topic on digestion, i have come up with a question: what are the organs that make digestion possible in our bodies? it may seem as though we have already learnt it in primary school. but in fact, human digestion is much more than that and there are still many interesting facts and details to it, which i am going to cover later on.

a very simple definition about digestion is that it is the breaking down of food in the body, into a form that can be absorbed into the blood stream, and the remainders that cannot be digested will then be passed out of the body.

let's take a look about the whole of the digestive system:

6:28 AM

my first entry

hi all, this will be my first post in this biology learning journal. the two topics that i have decided to work on are:

1. digestion
2. transport in living things

ok, that is all i have for now. the research that i have done for the two topics will be put on the next post. bye(: