Human Body: Cells, Tissues and Bones

A ribosome is the component of a biological cell that creates proteins from all amino acids and RNA representing the protein. One of the central tenets of biology, often referred to as the central dogma of molecular biology, is that DNA is used to make RNA, which is used to make protein.

Connective tissues are fibrous tissues. These are made up of cells separated by non-living material, which is called extracellular matrix. Connective tissue gives shape to organs and holds them in place. Both blood and bones are examples of connective tissue. As the name implies, connective tissue serves a connecting function. It supports and binds other tissues.

Simple cylindrical epithelial tissues can be found mainly in fallopian tubes, alimentary canal and small intenstine. Cells developing in fallopian tubes have cilia that make movements in uterus easier, and those developing in small intenstine contain microvilli that enlarge absorption surface. Cells of that tissue are prism-shaped. Nucelus is at the cell bottom.

Epithelial tissues in the kidney excrete waste products from the body and reabsorb needed materials from the urine. Sweat is also excreted from the body by epithelial cells in the sweat glands.

A mitochondrion is a membrane-enclosed organelle found in most eukaryotic cells. These organelles range from 0.5 to 10 micrometers in diameter. Mitochondria are sometimes described as cellular power plants because these generate most of the cell's supply of adenosine triphosphate (ATP), used as a source of chemical energy.

Mitochondria are found in both plant and animal cells and is the site of cellular respiration.They are rod-shaped organelles that can be considered the power generators of the cell, converting oxygen and nutrients into adenosine triphosphate (ATP). ATP is the chemical energy currency of the cell that powers the cell's metabolic activities.

The vomer is one of the unpaired facial bones of the skull. It is located in the midsagittal line, and articulates with the sphenoid, the ethmoid, the left and right palatine bones, and the left and right maxillary bones.

These are simple columnar epithelial cells, but in addition, they posses fine hair-like outgrowths, cilia on their free surfaces. These cilia are capable of rapid, rhythmic, wavelike beatings in a certain direction. This movement of the cilia in a certain direction causes the mucus, which is secreted by the goblet cells, to move (flow or stream) in that direction. Ciliated epithelium is usually found in the air passages like the nose. It is also found in the uterus and fallopian tubes of females. The movement of the cilia propels the ovum to the uterus.

White fibrocartilage is an extremely tough tissue. The orientation of the bundles depends upon the stresses acting on the cartilage. The collagenous bundles take up a direction parallel to the cartilage. Fibrocartilage is found as discs between the vertebrae between the pubic bones in front of the pelvic girdle and around the edges of the articular cavities such as the glenoid cavity in the shoulder joint.

The acrosome is an organelle that develops over the anterior half of the head in the spermatozoa (sperm cell) of many animals. It is a cap-like structure derived from the Golgi apparatus. Acrosome formation is completed during testicular maturation.

Bone plays a part in homeostasis because it helps to maintain a constant level of calcium in the blood.

Lysosomes are cellular organelles that contain acid hydrolase enzymes to break down waste materials and cellular debris. They are found in animal cells, while in yeast and plants the same roles are performed by lytic vacuoles.Lysosomes digest excess or worn-out organelles, food particles, and engulfed viruses or bacteria.

By virtue of the smooth surface of hyaline cartilage, it provides a sliding area which reduces friction, thus facilitating bone movement.

A myofibril is a basic unit of a muscle. Muscles are composed of tubular cells called myocytes or myofibers. Myofibers are composed of tubular myofibrils. Myofibrils are composed of long proteins such as actin, myosin, and titin, and other proteins that hold them together.

The lacrimal bone, the smallest and most fragile bone of the face, is situated at the front part of the medial wall of the orbit. It has two surfaces and four borders.

Ribosomes occur, both as free in the cytoplasm and as associated with endoplasmic reticulum. Ribosome are of 80 S kind. There are two subunits. Ribosomal RNA and proteins occur in the constitution of ribosomes.

 In plant cells, a large vacuole occurs which is surrounded by a semipermeable membrane called tonoplast. The membrane around vacuoles in animal cells is made up of lipoprotein. Normally, vacuoles do not occur in animal cells.

Nebulin is an actin-binding protein which is localized to the I-band of the sarcomeres in skeletal muscle. It is a very large protein (600-900 kDa) and binds as many as 200 actin monomers. Because its length is proportional to thin filament length, it is believed that nebulin acts as a thin filament ruler and regulates thin filament length during sarcomere assembly.

The part of the cell which occurs between the plasma membrane and nuclear envelope is called the cytoplasm. The cytoplasm is composed of the matrix, the organelles and non-living inclusions like vacuoles and granules.

Being a dynamic structure, it is quite flexible. Hence, it does not restrict growth, movements, and changes in the shape of a cell.

The cell membrane is a biological membrane that separates the interior of all cells from the outside environment. The cell membrane is selectively-permeable to ions and organic molecules and controls the movement of substances in and out of cells. It consists of the phospholipid bilayer with embedded proteins.