Feeds:
Posts
Comments

Archive for the ‘Biomaterials’ Category

 By: Sadwika Salain

Image source: www.cardiachealth.org

Artificial Valves

1         Introduction

Anatomically, the human heart comprises of four chambers—two atria and two ventricles. (Detail of the heart components is shown on figure 1). Physiologically, the heart can be considered as a positive displacement pump that generates blood flow to support systemic and pulmonary circulation. For this purpose, the heart undergoes both contraction and expansion in alternating period. It is estimated that the heart contracts and expands as many as on average 100,000 times everyday, pumping approximately 2,000 gallons of blood (Bender, 1992).

To ensure the blood flows in a forward direction, two valves at each ventricle – one at the inlet – open and shut in a synchronized manner. The four heart valves are:

  • Tricuspid valve : located between the right atrium and the right ventricle
  • Pulmonary valve : located between the right ventricle and the pulmonary artery
  • Mitral valve : between the left atrium and the left ventricle
  • Aortic valve : between the left ventricle and the aorta

The blood come from the veins, which has less oxygen, enters the heart via the right atrium. After filling, the right atrium then contracts and pushes the blood to the right ventricle through the tricuspid valve. From this ventricle, blood is sent to the lung through the pulmonary valve. In the lung the blood is oxygenated. Furthermore, the oxygenated blood returns to the left atrium then goes to the left ventricle through the mitral valve. The final stage is, the blood is squeezed out from the left atrium into the aorta and other circulatory system through the aortic valve. Detail of how the heart valve is working will be described in the following section. (more…)

Advertisements

Read Full Post »

stretchy

In the United States, the Food and Drug Administration (FDA) regulates condoms to ensure their safety and effectiveness. Different countries have different regulatory agencies. For example, condoms in Europe that have been properly tested and approved should carry the CE Mark. Elsewhere in the world, you can find that condoms are ISO approved. Also, individual countries may have their own approval marks for condoms, for example, the Kitemark in the UK. (more…)

Read Full Post »

1000 BC: Condom use can be traced back several thousand years. It is known that around 1000 BC the ancient Egyptians used a linen sheath for protection against disease.1 (more…)

Read Full Post »

Condom, as everyone knows, is a protective sheathe made from rubbery substance such as latex or polyurethane, close at one end and open at another. It protects the user from Sexually Transmitted Diseases (such as AIDS and many more) and helps in avoiding unwanted pregnancy. Condoms come in different sizes, shapes, colors, flavors etc. They also come with varying level of lubricants in them, and user even can choose a condom of his/her choice. But how many of us know about the history of condoms? Where did they come from? Who invented condoms? Who used it first? What kind of material was used for the first condom? Was lubrication used? If yes, then what substance was used as a lubricant? Etc. (more…)

Read Full Post »

Calcium Phosphate Coatings

Porous hydroxyapatite has been accepted that due to its unfavourable mechanical properties it cannot be used under load bearing purposes. For this reason hydroxyapatite has been used as thin film coatings on metallic alloys. Of the metallic alloys investigated titanium based alloys have shown to be the material of preference for thin film coatings. Titanium alloys possesses good mechanical strength and fatigue resistance under load bearing conditions. They are lightweight, with high strength to weight ratios. (more…)

Read Full Post »

Chemical formula

Ca10(PO4)6(OH)2

Background

Hydroxyapatite is chemically similar to the mineral component of bones and hard tissues in mammals. It is one of few materials that are classed as bioactive, meaning that it will support bone ingrowth and osseointegration when used in orthopaedic, dental and maxillofacial applications.

The chemical nature of hydroxyapatite lends itself to substitution, meaning that it is not uncommon for non-stoichiometric hydroxyapatites to exist. The most common substitutions involve carbonate, fluoride and chloride substitutions for hydroxyl groups, while defects can also exist resulting in deficient hydroxyapatites (more…)

Read Full Post »

Bone Cement Composites

During the last 5 years bone cement materials have grown in popularity and are very promising osteoconductive substitutes for bone graft. They are prepared like acrylic cements and contain a range of powders such as monocalcium phosphate, tricalcium phosphate and calcium carbonate, which is mixed in a solution of sodium phosphate. These cements are produced without polymerisation and the reaction is nearly non-exothermic. The final compounds are reported to have a strength of 10-100 MPa in compression while 1-10 MPa in tension, although very weak under shear forces. These composites are currently used in orthopaedics in the management of fractures. It has been suggested that these materials could improve the compressive strength of the vertebral bodies in osteoporosis. Injection of calcium phosphate cement has been shown to be feasible and it does improve their compressive strength. (more…)

Read Full Post »

Older Posts »