Human digestive system The human digestive system is a complex series of organs and glands that processes food. In order for the body to get the nutrients and energy it needs, food must be broken down into smaller molecules that can be absorbed into the bloodstream. The digestive system is made up of the mouth, esophagus, stomach, small intestine, large intestine, rectum, and anus. Mouth: The mouth is the first part of the digestive system. Here, food is chewed and mixed with saliva, which contains enzymes that help break down the food. Saliva also helps to moisten the food for easier swallowing. Human digestive system
Esophagus:
The esophagus is a long tube that connects the mouth to the stomach. Contractions of the muscles in the walls of the esophagus move food from the mouth to the stomach. Stomach: The stomach is a muscular sac that is responsible for the mechanical and chemical breakdown of food. The stomach secretes digestive juices, such as hydrochloric acid and powerful enzymes, that help break down the food. Small Intestine: The small intestine is a long, coiled tube that is responsible for the absorption of nutrients from food. After the food leaves the stomach, it enters
Structures And Functions Of The Human Digestive System
The human digestive system is composed of several organs that work together to break down food, absorb nutrients, and eliminate waste. The main structures and functions of the digestive system are Mouth: The mouth is the first part of the digestive system. It is responsible for the initial breaking down of food through the process of chewing and salivation. Saliva contains an enzyme called amylase, which breaks down carbohydrates. Esophagus: The esophagus is a tube-like structure that connects the mouth to the stomach. Its main function is to transport food from the mouth to the stomach.
Stomach:
The stomach is a muscular organ that is responsible for breaking down food through the process of digestion. It produces gastric juices, which contain acids and enzymes that help break down food. Small Intestine: The small intestine is a long tube-like structure that absorbs nutrients from food. It is divided into three sections: the duodenum, jejunum, and ileum. It is lined with small finger-like projections called villi, which increase the surface area and allow for more efficient absorption of nutrients. Large Intestine: The large intestine is a shorter tube-like structure that absorbs water and minerals from undigested food. It is also responsible for the formation of solid waste, which is then eliminated through the rectum and anus. Human digestive system
Liver:
The liver is the largest organ in the body and is responsible for producing bile, which helps break down fats in the small intestine. It also aids in the digestion of proteins and carbohydrates, and stores and metabolizes vitamins and minerals.
Gallbladder:
The gallbladder is a small organ located beneath the liver that stores and concentrates bile produced by the liver. Bile helps break down fats in the small intestine.
Pancreas:
The pancreas is a gland located behind the stomach that produces pancreatic juices, which contain enzymes that help break down carbohydrates, proteins, and fats.
Rectum and Anus:
The rectum and anus are the end components of the digestive system. The rectum stores solid waste that is eliminated through the anus.
Mouth and oral structures
Mouth:
The mouth is the opening of the digestive system, responsible for intake of food and liquid. Lips: The lips are two fleshy folds that surround the opening of the mouth. They are mainly responsible for helping to form words and for keeping food and liquid in the mouth.
Tongue:
The tongue is a muscular organ that helps to manipulate food in the mouth and helps in the formation of speech.
Teeth:
The teeth are the hard structures in the mouth that are use to bite and chew food. Gums: The gums are the soft fleshy structures that surround and protect the teeth.
Palate:
The palate is the roof of the mouth, which separates the oral cavity from the nasal cavity.
Salivary Glands:
The salivary glands are responsible for producing saliva, which helps to moisten food and aids in digestion.
Uvula:
The uvula is a small fleshy structure located at the back of the mouth that helps to direct food to the throat.
The lips and cheeks
The lips, the two fleshy folds that surround the mouth, are composed of skin on the outside and a mucous membrane, or mucosa, on the inside. The mucosa is rich in mucus-secreting glands, which together with saliva ensure adequate lubrication for speech and masticatory purposes.
Lips and cheeks are two prominent facial features in humans. The lips are fleshy, moist, and full of nerve endings, making them extremely sensitive to the touch. Cheeks are plump, round, and often rosy, giving the face a healthy, youthful appearance. They help make facial expressions, such as smiling and play an important role in expressing emotions.
The cheeks, and sides of the mouth, are continuous with the lips and have the same texture. A separate fat pad is found in the subcutaneous tissue (the tissue under the skin) of the cheek. This pad is especially large in infants and is known as the sucking pad. On the inner surface of each cheek, opposite the second upper molar, there is a slight elevation that marks the opening of the parotid duct, which originates from the parotid salivary gland located in front of the ear. Just behind this gland are four to five mucus-secreting glands whose ducts open in front of the last molar tooth.
The roof of the mouth
The roof of the mouth is concave and is form by the hard and soft palate. The hard palate is form by the horizontal parts of the two palatine bones and the palatine parts of the maxilla or upper jaw. The hard palate is cover by a thick, somewhat light mucous membrane that is continuous with the gingiva and is attach to the bones of the upper jaw and palate by strong fibrous tissue. The soft palate is continuous with the front hard palate. Laterally it is continuous with the mucous membrane covering the floor of the nasal cavity. The soft palate consists of a strong, thin, fibrous sheath, the palatine aponeurosis, and the glossopalatine and pterygopalatine muscles. A small projection called the uvula is free from the back of the soft palate.
The floor of the mouth
The floor of the mouth can only be see when the tongue is up. In the midline, there is a prominent, raise fold of mucous membrane (frenulum lingual) that connects each lip to the gingiva, and on each side is a slight fold call the sublingual papilla, which drains the submandibular saliva. The ducts of the glands open. Running outward and backward from each sublingual papilla is a ridge (plica sublingual) that marks the upper edge of the sublingual (under the tongue) salivary gland and onto which most of the gland’s ducts open.
The gums
The gums consist of mucous membranes that are attach to the membrane surrounding the jawbones by thick fibrous tissue. The gingival membrane forms a collar around the base of the crown (exposed part) of each tooth. Rich in blood vessels, the gingival tissues receive branches from the alveolar arteries. These vessels, called alveolar because of their relationship to the teeth of the alveoli, or tooth sockets, also supply the teeth and the spongy bone of the upper and lower jaws, in which the teeth are place.
The teeth
The teeth are hard, white structures are find in the mouth. Commonly used for mastication, the teeth of various vertebrate species are sometimes specialize. The teeth of snakes, for example, are very thin and sharp and usually curved backwards. They function in catching prey but not in chewing, as snakes swallow their food whole. Carnivorous mammals, such as cats and dogs, have sharper teeth than primates, including humans. Canines are longer, and premolars lack flat grinding surfaces, which are more adapt to biting and shaving (more posterior molars are often lost). On the other hand, herbivores such as cows and horses have very large, flat premolars and molars with complex and cusps. Dogs often disappear entirely. Sharp pointed teeth, poorly adapted for chewing, typically characteristic of carnivores such as snakes, dogs, and cats. and broad, flat teeth, well adapted for chewing, characteristic of herbivores.
Differences in tooth forms:
Differences in tooth forms are functional adaptations. Few animals can digest cellulose, yet plant cells use as food by herbivores contain cellulose enclose in cell walls that are expose to the action of enzymes that digest the cell material. should be broken before In contrast, animal cells in meat are not encased in indigestible matter and can be directly process by digestive enzymes. Consequently, chewing is not as important for carnivores as it is for vegetarians. Humans, who are herbivores (eating plants and animal tissue), have teeth that belong, functionally and structurally, somewhere between the extremes of specialization achieved by the teeth of carnivores and herbivores.
The root is the part of the jawbone that supports and strengthens the tooth in the jawbone. The shapes of crowns and roots vary between different parts of the mouth and from one animal to another. The teeth on one side of the jaw basically mirror the teeth on the opposite side. The upper teeth are distinct and complementary to the lower teeth. Humans usually have two sets of teeth in their lifetime. The first set, known as the deciduous, milk, or primary teeth, are gradually acquire between the ages of six months and two years. As the jaws grow and expand, these teeth are replace one by one by the secondary set of teeth. Each quarter of the mouth has five canines and eight permanent teeth, resulting in a total of 32 permanent teeth after 20 deciduous teeth.
Salivary glands
Food is tasted and mixed with saliva, which is secreted by several sets of glands. In addition to the many minute glands that secrete saliva, there are three major pairs of salivary glands: the parotid, submandibular, and sublingual glands. The parotid glands, the largest of the glands, are located on one side of the face, below and in front of each ear. The parotid glands are enclosed in sheaths that limit the extent of their swelling when they become inflamed, as in mumps. The submandibular glands, which are round in shape, are located near the inside of the lower jaw bone, in front of the sternomastoid muscle (prominent jaw muscle). The sublingual glands lie directly under the tongue under the mucous membrane that covers the floor of the mouth.
Salivary glands
Salivary glands are of the type call racemose, from the Latin racemosus (“full of clusters”), because of the cluster-like arrangement of their secretory cells in round sacs, call acini, independent of ducts. but are connect by a system of branches. The walls of the acini surround a small central cavity called the alveolus. The walls of the acini contain pyramidal-secreting cells and some flat, star-shaped contractile cells called myoepithelial, or basket, cells. The latter cells are thought to contract like similar myoepithelial cells of the breast, which by their contraction expel milk from the milk ducts.
Secretory cells can be serous or mucous type. The latter type secretes mucin, the main component of mucus. The secretory cells of the parotid gland are of serous type. Of the submandibular glands, both serous and mucous, serous cells outnumber mucous cells four to one. The acini of the sublingual glands are mainly composed of mucous cells.