endocrine alimentary system all parts and there introduce definition and function parts andrenal glands adrenal medulla pancreas stomach liver duodenum kidney

1--Adrenal glands

In mammals, the adrenal glands (also known as suprarenal glands) are endocrine glands that sit atop the kidneys; in humans, the right suprarenal gland is triangular shaped, while the left suprarenal gland is semilunar shaped. They are chiefly responsible for releasing hormones in response to stress through the synthesis of corticosteroids such as cortisol and catecholamines such as epinephrine. The adrenal glands affect kidney function through the secretion of aldosterone, a hormone involved in regulating the osmolarity of blood plasma.

Anatomy and function

Anatomically, the adrenal glands are located in the retroperitoneum situated atop the kidneys, one on each side. They are surrounded by an adipose capsule and renal fascia. In humans, the adrenal glands are found at the level of the 12th thoracic vertebra. Each adrenal gland has two distinct structures, the adrenal cortex and the medulla, both of which produce hormones. The cortex mainly produces cortisol, aldosterone and androgens, while the medulla chiefly produces epinephrine and norepinephrine. The combined weight of the adrenal glands in an adult human ranges from 7 to 10 grams.


2---Adrenal medulla

The adrenal medulla is part of the adrenal gland. It is located at the center of the gland, being surrounded by the adrenal cortex. It is the innermost part of the adrenal gland, consisting of cells that secrete epinephrine, norepinephrine, and a small amount of dopamine in response to stimulation by sympathetic preganglionic neurons.

Basic

The adrenal medulla consists of irregularly shaped cells grouped around blood vessels. These cells are intimately connected with the sympathetic division of the autonomic nervous system (ANS). In fact, these adrenal medullary cells are modified postganglionic neurons, and preganglionic autonomic nerve fibers lead to them directly from the central nervous system.

Function

Rather than releasing a neurotransmitter, the cells of the adrenal medulla secrete hormones.

Composed mainly of hormone-producing chromaffin cells, the adrenal medulla is the principal site of the conversion of the amino acid tyrosine into the catecholamines adrenaline (epinephrine), noradrenaline (norepinephrine), and dopamine.

Because the ANS exerts direct control over the chromaffin cells the hormone release can occur rather quickly. In response to stressors such as exercise or imminent danger, medullary cells release catecholamines into the blood in a 17:3 ratio of adrenaline to noradrenaline.

Notable effects of adrenaline and noradrenaline include increased heart rate and blood pressure, blood vessel constriction in the skin and gastrointestinal tract, blood vessel dilation in skeletal muscles, bronchiole dilation, and decreased metabolism, all of which are characteristic of the fight-or-flight response. Release of catecholamines is stimulated by nerve impulses, and receptors for catecholamines are widely distributed throughout the body.

3--Pancreas

The pancreas is a gland organ in the digestive and endocrine system of vertebrates. It is both an endocrine gland producing several important hormones, including insulin, glucagon, and somatostatin, as well as an exocrine gland, secreting pancreatic juice containing digestive enzymes that pass to the small intestine. These enzymes help to further break down the carbohydrates, proteins, and lipids in the chyme.


4---Stomach

The stomach is a muscular, hollow, dilated part of the alimentary canal which functions as an important organ of the digestive tract. It is involved in the second phase of digestion, following mastication (chewing). The stomach is located between the oesophagus and the small intestine. It secretes protein-digesting enzymes and strong acids to aid in food digestion, (sent to it via oesophageal peristalsis) through smooth muscular contortions (called segmentation) before sending partially-digested food (chyme) to the small intestines.

The word stomach is derived from the Latin stomachus which is derived from the Greek word stomachos, ultimately from stoma, "mouth". The words gastro- and gastric (meaning related to the stomach) are both derived from the Greek word gaster (?ast??).

Role in digestion

Bolus (masticated food) enters the stomach through the oesophagus via the oesophageal sphincter. The stomach releases proteases (protein-digesting enzymes such as pepsin) and hydrochloric acid, which kills or inhibits bacteria and provides the acidic pH of 2 for the proteases to work. Food is churned by the stomach through muscular contractions of the wall - reducing the volume of the fundus, before looping around the fundus and the body of stomach as the boluses are converted into chyme (partially-digested food). Chyme slowly passes through the pyloric sphincter and into the duodenum, where the extraction of nutrients begins. Depending on the quantity and contents of the meal, the stomach will digest the food into chyme anywhere between 40 minutes and a few hours.

Anatomy of the stomach

The stomach lies between the oesophagus and the duodenum (the first part of the small intestine). It is on the left upper part of the abdominal cavity. The top of the stomach lies against the diaphragm. Lying behind the stomach is the pancreas. The greater omentum hangs down from the greater curvature.

Two sphincters keep the contents of the stomach contained. They are the esophageal sphincter (found in the cardiac region, not an anatomical sphincter) dividing the tract above, and the Pyloric sphincter dividing the stomach from the small intestine.

The stomach is surrounded by parasympathetic (stimulant) and orthosympathetic (inhibitor) plexuses (networks of blood vessels and nerves in the anterior gastric, posterior, superior and inferior, celiac and myenteric), which regulate both the secretions activity and the motor (motion) activity of its muscles.

In adult humans, the stomach has a relaxed, near empty volume of about 45 ml. Because it is a distensible organ, it normally expands to hold about 1 litre of food, but can hold as much as 2-3 litres. The stomach of a newborn human baby will only be able to retain about 30ml.

5--Liver

The liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion. The liver is necessary for survival; there is currently no way to compensate for the absence of liver function long term, although liver dialysis can be used short term.

This organ plays a major role in metabolism and has a number of functions in the body, including glycogen storage, decomposition of red blood cells, plasma protein synthesis, hormone production, and detoxification. It lies below the diaphragm in the abdominal-pelvic region of the abdomen. It produces bile, an alkaline compound which aids in digestion via the emulsification of lipids. The liver's highly specialized tissues regulate a wide variety of high-volume biochemical reactions, including the synthesis and breakdown of small and complex molecules, many of which are necessary for normal vital functions.


6--Duodenum

The duodenum is the first section of the small intestine.

The duodenum is largely responsible for the breakdown of food in the small intestine, using enzymes. Brunner's glands, which secrete mucus, are found in the duodenum. The duodenum wall is composed of a very thin layer of cells that form the muscularis mucosae. The duodenum is almost entirely retroperitoneal.

The duodenum also regulates the rate of emptying of the stomach via hormonal pathways. Secretin and cholecystokinin are released from cells in the duodenal epithelium in response to acidic and fatty stimuli present there when the pylorus opens and releases gastric chyme into the duodenum for further konadigestion. These cause the liver and gall bladder to release bile, and the pancreas to release bicarbonate and digestive enzymes such as trypsin, lipase and amylase into the duodenum as they are needed.


7--Kidney

The kidneys, organs with several functions, serve essential regulatory roles in most animals, including vertebrates and some invertebrates. They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid-base balance, and regulation of blood pressure (via maintaining salt and water balance). They serve the body as a natural filter of the blood, and remove wastes which are diverted to the urinary bladder. In producing urine, the kidneys excrete wastes such as urea and ammonium; the kidneys also are responsible for the reabsorption of water, glucose, and amino acids. The kidneys also produce hormones including calcitriol, renin, and erythropoietin.

Located at the rear of the abdominal cavity in the retroperitoneum, the kidneys receive blood from the paired renal arteries, and drain into the paired renal veins. Each kidney excretes urine into a ureter, itself a paired structure that empties into the urinary bladder.

Renal physiology is the study of kidney function, while nephrology is the medical specialty concerned with kidney diseases. Diseases of the kidney are diverse, but individuals with kidney disease frequently display characteristic clinical features. Common clinical conditions involving the kidney include the nephritic and nephrotic syndromes, renal cysts, acute kidney injury, chronic kidney disease, urinary tract infection, nephrolithiasis, and urinary tract obstruction. Various cancers of the kidney exist; the most common adult renal cancer is renal cell carcinoma. Cancers, cysts, and some other renal conditions can be managed with removal of the kidney, or nephrectomy. When renal function, measured by glomerular filtration rate, is persistently poor, dialysis and kidney transplantation may be treatment options. Although they are not severely harmful, kidney stones can be a pain and a nuisance. The removal of kidney stones includes sound wave treatment, which breaks up the stones into smaller pieces which are then passed through the urinary tract. One common symptom of kidney stones is a sharp pain in the medial/lateral segments of the lower back.