Human sperm cells attempting to fertilize an egg cell (ovum). Photo Credit: Renjith Krishnan FreeDigitalPhotos.net

In sexual reproduction, male sperm must navigate the female reproductive tract in order to fertilize the egg cell (ovum). Researchers have discovered how sperm make their way to the egg. Contrary to popular notion, they don't swim in the center of the reproductive tract. Instead, they travel along the walls of the reproductive tract, maneuvering complex channels, often colliding into walls. Of the millions of sperm that are released into the reproductive tract, only about ten reach the egg cell.

In the study, the researchers examined sperm behavior by injecting sperm into extremely small micro-channels. Researcher Dr. Kirkman-Brown states, "Through research like this we are learning how the good sperm navigate by sending them through mini-mazes. Previous research from the group indicates that the shape of the sperm head can subtly affect how the sperm swim." Learning about how sperm make their way to an egg may help to develop methods for identifying qualities in sperm that make them more capable of reaching and fertilizing an egg. Studies such as this one may provide insight into the development of new methods of treating infertility.

Learn more about this study, see:

• Sperm Crawl and Collide On Way to Egg, Say Scientists (Science Daily)

Credit: Worakit Sirijinda / FreeDigitalPhotos.net

University of Texas at Austin researchers have determined that body mass and maximum running speed are the two most important factors that determine eye size in mammals. The researchers believe that fast mammals such as cheetahs and horses have larger eyes for better vision when moving at a high rate of speed. This helps them to avoid collisions.

According to researcher Chris Kirk, "There is going to be the effect of body mass, but when you look at maximum running speed in isolation or when you hold body mass constant, it's still significantly related to eye size. And when you combine maximum running speed and body mass as your two variables influencing how big an eye is, they can explain almost all of the differences observed between species." This discovery challenges the previous thought that the main factor influencing mammalian eye size is the time of day when the animal is active. That is, whether an animal is nocturnal or diurnal.

Learn more about this study, see:

• Eye Size Determined by Maximum Running Speed in Mammals (Science Daily)

This image shows Listeria infecting human cells. Image: Keith Ireton / University of Central Florida

Manchester University researchers are attempting to combat antibiotic resistance by developing a way to prevent bacteria from infecting cells of the body. While studying a group of bacteria called Listeria, the researchers discovered that they spread infection through a cell protein called calpain. Learning about how bacteria spread infection could lead to the development of new anti-infective drugs that could be an alternative to antibiotics.

According to lead researcher Dr. David Brough, "We have investigated the growth of Listeria, a pathogenic bacterium that grows inside cells. An essential step for its growth, and thus the infection, is the bacteria's ability to move from within one compartment in a cell to another. We discovered that in order for this particular type of bacteria to move and to grow some of the host cells biology is exploited, a protein called calpain. Without calpain the bacteria cannot move within the cell and so do not grow." The researchers contend that drugs could potentially be developed against the protein to inhibit infection. This would reduce the necessity for antibiotic use.

Learn more about this study, see:

• Bacteria Discovery Could Lead to Antibiotics Alternatives (Science Daily)

Image: Rod Nave

Constructing a lung model is an excellent way to learn about the respiratory system and lung function. The lungs provide a place for gas exchange between air from the outside environment and gases in the blood. The respiratory and cardiovascular systems work together to obtain and circulate gases throughout the body. The heart pumps de-oxygenated blood to the lungs through the pulmonary arteries. Oxygen is picked up in the lungs and the newly oxygenated blood returns to the heart via the pulmonary veins.

Breathing is controlled by a region of the brain called the medulla oblongata. The brain sends signals to muscles in the diaphragm causing them to contract. This contraction causes inhalation and creates low pressure in the chest cavity. As the diaphragm relaxes, pressure within the chest cavity increases resulting in exhalation. In this lung model demonstration, structures of the respiratory system will be represented as follows:

• plastic bottle = chest cavity
  
• plastic tubing = trachea
  
• Y-shaped connector = bronchi
  
• balloons inside bottle = lungs
  
• balloon covering bottom of bottle = diaphragm

For additional information about biology models and experiments see: DNA Models, How To Make a DNA Model Using Candy and How To Extract DNA From a Banana.