Category Human Body

This magnified image of a scan shows a cut away in the deeply folded lining of the duodenum, the first section of the small intestine. The folds are called villi, and these greatly increase the area of the lining – creating a larger surface through which food nutrients can be absorbed.

Nutrients from food are absorbed by microvilli on the surface of the villi, shown here as a green, fur-like layer. Nutrients then pass through a layer of cells (shown in blue-green) before being carried away by blood vessels in in the middle.

Their function is to increase the surface area of the small intestinal wall for absorption of the digested food. These projections absorb the protein molecules and help in the transfer of the proteins to all cells and tissues. Many blood vessels are present within these villi, that help in the absorption of digested food and carry it to the bloodstream. Later, from the bloodstream, the absorbed food is delivered to each and every cell of the body.

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Bundled up

The small intestine is at the front of the lower abdomen, surrounded by the large intestine and other organs. Although it’s very long – more than 6 m (20 ft) – the small intestine fits into this space because it is bundled up in a series of loops and coils.

Duodenum

The first part of the small intestine is where bile and enzymes are added to the chyme to help break it down. It extends from the pyloric sphincter of the stomach, wraps around the head of the pancreas in a C-shape and ends at duodenojejunal flexure. The duodenum has four parts: superior (duodenal bulb/ampulla), descending, horizontal and ascending. 

Jejunum

This is the middle section of the small intestine, where most of the digestion and absorption of food takes place. The jejunum is entirely intraperitoneal as the mesentery proper attaches it to the posterior abdominal wall.

Ileum

The final, longest section of the small intestine absorbs some nutrients. It is found in the lower right quadrant of the abdomen, although the terminal ileum can extend into the pelvic cavity. The ileum terminates at the ileal orifice (ileocecal junction) where the cecum of the large intestine begins.

lleocaecal valve

The ileocecal valve is a sphincter muscle situated at the junction of the ileum (last portion of your small intestine) and the colon (first portion of your large intestine). Its function is to allow digested food materials to pass from the small intestine into your large intestine. Chyme from the small intestine passes through here to the large intestine.

Looking inside

A cross-section through part of the small intestine shows the muscles that help to push food along its length. The lining is covered with millions of tiny finger-like projections called villi (a single projection is a villus).

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The small intestine is the longest part of the digestive system. It’s where most of the digestive process takes place, releasing the nutrients in food so that they can be used to fuel the body’s cells.

By the time food reaches the small intestine, the stomach has turned it into a liquid called chyme. This chyme is squirted into the duodenum, the first part of the small intestine, along with bile from the gallbladder and enzymes from the pancreas, which break the chyme down even more. Finally, when most of the food has been broken down into simple nutrients, these pass through the walls of the small intestine and into the bloodstream. The remaining food progresses to the next stage – the large intestine.

As a person grows the small intestine increases 20 times in length from about 200 cm in a newborn to almost 6 m in an adult. The length of the small intestine is approximated by three times the length of the infant, or height of the child or adult.

The duodenum is about 25 cm (10 inches) long; the jejunum is about 2.5 m (8 feet) long and the ileum is about 3.6 m (12 feet) long.

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Ligaments are made out of connective tissue that has a lot of strong collagen fibers in it. They are found in different shapes and sizes in the body. Some look like pieces of string, others look like narrow or wide bands. There are arch-shaped ligaments, too.

Ligaments often connect two bones together, particularly in the joints: Like strong, firmly attached straps or ropes, they stabilize the joint or hold the ends of two bones together. This ensures that the bones in the joint don’t twist too much or move too far apart and become dislocated.

But there are also some ligaments that aren’t connected to bones. For instance, some make sure that internal organs are kept in place. A typical example is the womb, which is kept in the right position in the pelvis by ligaments. Ligaments may also connect two or more organs to each other. For instance, the liver, intestine and stomach are held in place by ligaments in the abdominal cavity. These ligaments often have sensitive structures like blood vessels or gland ducts running through them. The strong connective tissue in the ligaments protects these structures and prevents them from bending, twisting or tearing.

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The ossicles are situated in the middle ear and suspended by ligaments. They articulate with each other through synovial joints to form a chain across the length of the middle ear from the tympanic membrane (laterally) to the oval window (medially). The ossicles transmit mechanical vibrations of the tympanic membrane across this chain to the oval window where fluids of the inner ear will move and excite receptors. This process allows sound to be transformed into electrical signals which are then sent to the brain.  This article will explore the function of the auditory ossicles, their bony features, articulations, associated muscles, and some clinical aspects.

Their role is to mechanically amplify the vibrations of the tympanic membrane and transmit them to the cochlea where they can be interpreted as sound. They are located in the middle ear cavity and articulate with each other via two tiny synovial joints. The stapes also articulates with the oval window via the stapediovestibular joint, which is a syndesmosis 3; this joint transmits the ossicular vibrations to the endolymph in the vestibule.

Interestingly, they are the only bones in the body that do not grow after birth, and are also the smallest bones in the body (variant tiny sesamoids aside).

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Bone marrow is the spongy tissue inside some of the bones in the body, including the hip and thigh bones. Bone marrow contains immature cells, called stem cells.

Most red blood cells, platelets, and most of the white blood cells are formed in the red marrow. Yellow bone marrow produces fat, cartilage, and bone.

White blood cells survive from a few hours to a few days, platelets for about 10 days, and red blood cells for about 120 days. These cells must be constantly replaced by the bone marrow, as each blood cell has a set life expectancy.

Certain conditions may trigger additional production of blood cells. This may happen when the oxygen content of body tissues is low, if there is loss of blood or anemia, or if the number of red blood cells decreases. If these happen, the kidneys produce and release erythropoietin, a hormone that stimulates the bone marrow to produce more red blood cells.

The bone marrow also produces and releases more white blood cells in response to infections, and more platelets in response to bleeding. If a person experiences serious blood loss, yellow bone marrow can be activated and transformed into red bone marrow.

Healthy bone marrow is important for a range of systems and activities.

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