Salivary Glands

Concerning the salivary glands definition, these are glandular structures present at various locations in and around the oral cavity, they are responsible for the secretion of important digestive enzymes and fluids that help in the digestion and lubrication of dietary substances in your mouth. Ptyalin or salivary amylase and lipase are secreted by these ducted exocrine glands and are responsible for the oral digestion of food. Composed of cluster of secretary cells, called acini, they also synthesize mucous, water and electrolytes that are then released into the collecting ducts. Among the different types of salivary glands, submandibular, sublingual and parotid are more important as each of which is assigned a particular task to perform. The large particles of food are ground into smaller ones that are then moistened and converted into a semi-solid mass of partly digested food (almost round in shape) which you tem as 'bolus'. Some painful medical condition may arise out of the malfunctioning of salivary glands which cause severe disturbances in the region but can easily be relieved through various treatment measures.

Based on their function and particular location in and around the mouth cavity, the saliva secreting organs can be divided into different types, viz. sublingual glands, submandibular glands, Von Ebnor's glands, parotid glands and minor salivary glands. Parotid is present behind the mandibular ramus and constitutes the largest of salivary glands that releases its serous secretions into the oral chamber through Stensen's duct. Pouring the mucus and serous fluids into the mouth through Wharton's duct, the submandibular glands are found beneath the jaws. As the very name suggests, sublingual glands are located beneath the tongue and contribute about five percent of the salivary secretions in the oral chamber. Scattered across mucosa in the mouth, there are about 800 to 1000 minor salivary gland parts or that are surrounded by connective tissue and secrete mucous that is delivered to the oral cavity through a shared excretory duct.

Spinal Cord

Measuring up to 18 inch in length, the dorsal neural tube gradually decreases in width while running downwards in the vertebral column, i.e. at the cervical regions the thickness is about 1/2 inch while reaching the lumbar vertebrae the size is reduced to just 1/4 inches in diameter. However, it is comparatively shorter in length than your bony spinal column and does not run along its entire length. On the whole, the ovoid structure of neural tube can be subdivided into 33 segments in human beings. Based on their association with the different regions of vertebrae, these segments can be grouped into five broader categories which are briefly described as under:

Cervical Segments

Being the anterior most segments of the spinal cord that run across seven cervical vertebrae, it is located along the neck region. The upper portion forms as many as eight pairs of cervical nerves which are named with the vertebra they emerge from, viz. C1, C2, C3, C4, ? C8. However, the C8 pair of cervical nerve emerges from the lower end of the C7 vertebral segment while all of other pairs emerge from the upper end of the respective vertebra.

Thoracic Segments

Running along the series of twelve T vertebrae in the thoracic region, they constitute 12 pairs of thoracic nerves each of which leaving the vertebral column below the associated vertebral division.

Lumbar Segments

It is one of the parts of spinal cord that is protected by five lumbar vertebrae, it gives rise to five pairs of nervous extensions each of which emerges below the associated vertebra.

Control of Reflexes
Another major task of this part of your CNS is the independent control and coordination of central nerve generators and certain reflexes. Such actions protect your body against dangerous stimuli by the generation and application of a quick response. Under such circumstances, the prolongation of response may inflict an irreparable damage to your body.

Ailments of the spinal nerve column are generally referred to as the disorders of central nervous system as it is its second major component. Besides injuries, a number of diseases have been identified affecting the region, viz. infections, inflammations, tumors, and degenerative disorders. Such spinal abnormalities are revealed through different clinical manifestations, like the loss of sensation, numbness, severe pain, and muscle weakness. The symptoms usually occur around the spinal cord but may also spread to arms and legs. For their amelioration, your health care provider may advise you different treatment measures mainly depending on the type and severity of the disorder, but the most frequently recommended strategies include drug administration and surgical therapy.

Trachea

Concerning trachea definition, it is an important anatomical structure that is an integral part of respiratory system in humans and other higher animals. Allowing the passage of air (respiratory gases) it connects larynx (voice box) and pharynx with lungs. The trachea location can be traced in the chest region, and it is made of soft bony material, called cartilage that allows great amount of flexibility for the efficient performance of its essential tasks. However, as the age progresses, it becomes rigid and hard, and is converted into bone. Apart from just gaseous exchange, it is also involved in the production of vocal sounds as one of the secondary trachea functions. As with other organs of your body, trachea is also vulnerable to a number of diseases that are commonly known as respiratory disorders, viz. tracheal stenosis, tracheobronchomalacia,

As you can see in the trachea pictures, the windpipe is structurally composed of incomplete rings, resembling the letter C in English which range from 15 to 20 in number. At the anterior end, the air passage is bound by a membranous structure, called larynx that contains vocal chords running horizontally across its mouth and forming voice apparatus in humans for the production of speech sounds. At the posterior end, it undergoes dichotomous branching, thus dividing into the two smaller tubes, viz. primary bronchi. Each of the primary bronchi runs into either of the lungs (i.e. left or right one) and allows the smooth and efficient passage of air (or the exchange of respiratory gases). Going deeper into lungs, further branching takes place in which bronchi are subdivided into bronchioles ultimately attaining the size of very small air sacs enclosed by respiratory membranes through which exchange of respiratory gases (carbon dioxide & oxygen) virtually takes place. With the help of incomplete rings, the anterior of the tube (lumen) can be narrowed down to accelerate the air passing through it when needed, e.g. while coughing.

Any ailment of the respiratory system may disturb the overall functioning of your body as it is responsible for the facilitation of the process of energy extraction from food. Forming front tubular part of the respiratory system, the anatomical structure, if attached by some acute or chronic disorder, results in the partial or complete collapse of airway system and often leads to the death of the individual. It is surprising to know that this is the organ system of your body which is exposed and extremely vulnerable to environmental hazards, especially in this highly polluted atmosphere. A number of tracheal ailments may arise out of various factors, like infectious and hereditary which include inflammation, tumor formation, cancerous outgrowth, obstructive disorders, etc. Tracheal stenosis is characterized by inflammation of the windpipe that may be relieved by endoscopy or surgical therapy. Formation of large tumor (benign or cancerous) in the lumen of trachea may cause the blockage of the air passage and death of the victim due to chocking. Though it is very difficult to avoid contact with respiratory diseases, proper care, preventive measures and early treatment of the abnormalities can save you from life long miseries.

Ears

As you can see in the human ear diagram, it is designed in such a way that it captures the maximum auditory stimuli from the atmosphere and transfers them to the brain for translating into hearing response. Three major parts of a human ear are the outer, middle and inner respectively, each having its own functions, anatomy and ear diseases as well.

The external ear anatomy is the study of the parts of the outer ear. There are two major parts of the external ear, i.e. the pinna and the external acoustic meatus. Pinna or the auricle lies externally and its main job is to capture the sound waves and transmit them to the external acoustic meatus. Most of the framework of the auricle is cartilaginous in nature. Here lobule is the only structure which does not have the support of cartilage.

The external acoustic meatus, on the other hand, is a tube like structure that extends from the middle hollow depression or concha of the auricle. At the other end, it reaches the tympanic membrane. It has a cartilaginous structure and gets the bony support from the temporal bone. The branches of vagus and mandibular nerves provide sensory innervation to this particular part of your external ear.

Do you know if the external acoustic meatus travel in the straight path? Well, this is not the case. In fact, it has got an S-shaped path.

⇛ Link between Cold and Dumbness: Do you know about one of the amazing ear facts that there is a connection between the middle ear and the throat? This connection develops through a tube, i.e. the Eustachian tube. This is the very reason behind your going dumb every time you catch cold. The main function of the tube is to equalize the pressure between the atmosphere and the body.

⇛ Disturbance in Equilibrium: At higher pressures, and on mountain tops, it is common for people to go dumb. Meanwhile, they experience a disturbing feeling in their ears. It is because the Eustachian tube is unable to maintain equilibrium in body pressure.

⇛ Strength of Temporal Bone: According to the opinion of many people, femur is the hardest, longest and strongest bone in human body. But it does mean that the temporal bone is less in strength, i.e. it is equally hard and strong.

⇛ Remove Wax & Damage The Ear: Ear produces its own wax to protect itself from friction and dust. So, if you make frequent attempt to remove this wax, it may damage the tympanic membrane in the ears causing deafness.

Do you know exactly how the ear works? The sound waves that strike at the ear drum set it on vibration. This vibration then travels to the three small bones of the middle ear, (the malleus, stapes and incus). The bones of the middle ear, on the other hand, make specific movements and hit at the oval window.

Different parts of the ear and their functions are very important for hearing. The vestibular window separates the middle ear from the inner ear. The inner ear is also termed as cochlea, which is a dual membrane delicate structure, with fluids filled between the membranes and lined with hair cells. The movement of the hair cells that line cochlea, in response to the sound waves, is like that of grasses in the meadows. It serves to sends electrical impulses to the brain, i.e. the master organ, that accurately identifies the sounds we hear.

Rectum

The straight part of the colon is the dilated pouch like structure that is preceded by sigmoid colon and followed by anal canal. Before you defecate, the feces is temporarily stored in this gastrointestinal structure which becomes dilated on the arrival of waste material and induces the urge for its elimination through anal verge. The word "rectum" has been derived from a Latin phrase "Rectum Intestinum" which means "straight intestine". As the rectum facts suggest, this organ is about 12 cm in length, and begins at the third sacral vertebrae and is joined with the preceding section of large bowel at rectosigmoid junction. Based on the structure and function of the distal end of large gut, you can divide rectum parts

The primary rectum function is the temporary storage of stool so that you may have some time to reach the place where it can be defecated. As the waste and indigestible materials get entry into it, the canal becomes dilated, thus stretching the muscles lining the rectal region. Stretch receptors are located in the wall of rectum which sense the dilation of the gut and send signal to the nervous system (brain) where these are processed and a response is generated that induces the need for the elimination of waste materials passing through anal canal and getting out through anal verge. However, if you do not go for defecation for a prolonged duration, the stool gets back into the colon for further absorption of fluids which may also result in hardening of stool and constipation.

Small Intestine

Small Intestine Function

Functionally, you will find small gut very important part of gastrointestinal tract as it not only digests major part of the dietary contents but is also meant for absorbing finally broken down food particles. Meanwhile, you cannot underestimate the importance of large intestine and anus function. It’s the place where almost all of the absorption takes place including nutrients, bile salts, vitamins, and so on. Some of the major small intestine function can be listed as under:

Neutralization

The partly digested food that is coming from stomach through pyloric opening is highly acidic in its medium, but the enzymes present in duodenum and other parts of the canal cannot perform their activity as biological catalysts. So as the first and foremost function of the gut, this medium is neutralized and the enzymes are made to act in the most efficient way.

Digestion

After the medium has been made feasible for the enzymatic actions, the digestion of the remaining contents of chyme is accomplished here. As a part of overall small intestine function, different secretions are poured into canal, like bile and pancreatic juice that facilitate the process of breakdown to a greater extent, until the finally digested food particles are ready to be absorbed.

Absorption

Here it is surprising to know that among all the segments of gut, this is the only portion where almost all of the absorption and assimilation of digested food, vitamins and salts, takes place. For the intake of nutrients into the bloodstream, there are specialized cells (e.g. enterocytes) that facilitate the process of absorption. After entering the bloodstream, the food particles are delivered to all the living cells in the body where, by means of metabolic reactions, energy is extracted to accomplish all the vital activities.

Parts of Small Intestine

To enjoy an ideal health and counter the diseases, you must have sound knowledge of different parts of the body with facts. Small bowel is further divided into three structurally and somewhat functionally distinguishable smaller segments, viz. duodenum, jejunum and ileum. In various segments, the three layers of its wall are similar throughout its length, but there do exist certain structural differences among them.

Duodenum
The foremost and shortest part, it is functionally very important as major portion of the chemical digestion takes place here. Varying in length from 10 to 15 centimeter, it is, on the anterior end, connected with stomach, while the posterior end touches jejunum.

Jejunum
Constituting the second part of your small bowel, located between duodenum and ileum, it has the average length of about 8.4 feet or two and a half meter in adult humans. The pH of the medium inside this part of gut may vary between neutral to slightly alkaline, i.e. 7 to 9. The enterocytes are the specialized cells present in the lining of the canal that are actively involved in the absorption of small particles of food that were digested by enzymes in duodenum.

Ileum
This final section of small gut, on one hand, continues with jejunum, while on the other, it makes a connection with colon through ileocecal valve. In adult humans, it may vary from 7 to 14 feet in length, and the pH of the medium is same as that of jejunum which is neutral to a bit alkaline. Its major function is to absorb any nutrients that were not absorbed in the preceding sections of the gut. However, it is particularly involved in the absorption of bile salts and vitamins

Pancreas

Pancreas is one of the extrinsic glands of the digestive system. It has mixed endocrine and exocrine functions, and is present outside the wall of the digestive tract. In order to fully understand, "What is pancreas?" you must know its location, functions and diseases. The exocrine part secrets pancreatic juice into the duodenum; the juice contains a number of digestive enzymes and pro enzymes that help digest the food. The endocrine part produces hormones such as insulin that play significant role in the absorption, metabolism and storage of nutrients such as glucose. Dysfunction in the endocrine part of the pancreas leads to diabetes mellitus.

 A normal pancreas is about 12 to 15 cm long and weighs about 110 gm. Pancreas location is behind the stomach and it lies more or less transversely in the posterior wall of the abdomen; it has duodenum on its right and spleen on its left. It has a head that lies within the curvature of the duodenum, a neck that connects the head to the body and a body that blunts into its tail to touch the spleen. Cancer of the pancreas usually involves the head and accounts for most of the cases of extrahepatic biliary obstruction.

About 1500 ml of pancreatic juice is secreted everyday which contains many digestive enzymes, water and various ions such as bicarbonate, sodium, potassium.

pH of the pancreatic juice is alkaline in nature which helps neutralize the gastric content entering the duodenum from the stomach.

Pancreatic enzymes and pro-enzymes (zymogens) are essential for the digestion of protein, carbohydrate and fat constituents of food that we eat every day.

Endocrine part of pancreas secrets two important hormones - insulin and glucagon - both of which are secreted reciprocally from pancreas and also act reciprocally in most circumstances. In a nutshell, insulin increases storage of glucose, fatty acids and amino acids. On the other hand glucagon is a catabolic hormone so it mobilizes glucose, fatty acids and amino acids from stores into the bloodstream.

Secretion of the pancreatic juice is primarily regulated by two hormones -

Secretin

Cholecystokinin (CCK)

Both of these hormones are produced by specialized cells of the duodenum. They are secreted in response to gastric acid entering the duodenum from the stomach and in response to products of protein and fat digestion (e.g. small peptides, amino acids and fatty acids). Both hormones act synergistically in response to a meal and cause a large volume of alkaline pancreatic juice rich in digestive enzymes to be released.