Physiology and Function in Human

Physiology and Function in Human Digestion

Describe the relationship among parathyroid hormone, vitamin D3 (cholecalcierol), liver, and kidney.

Parathyroid hormone is important for the intestinal absorption of calcium through the synthesis of vitamin D Specifically, it regulates the enzyme necessary for converting vitamin D to its active form in the kidneys, which in turn, increases calcium absorption in the intestine. The liver is responsible for selective extraction of parathyroid hormone while the kidney is exclusively responsible for fragmentary removal.

Describe the two major types of adrenocortical hormones and their functions.

The two main types of adrenocortical hormones are glucocorticoids and mineralocorticoids. Glucocorticoids play numerous roles in the human endocrine system, including the regulation of sodium and potassium which are crucial for normal fluid balance, blood pressure, and proper circulation. Cortisol in particular regulates the metabolism of nutrients and glucose production by the liver. Mineralocorticoids such as aldosterone, progesterone, and deoxycorticosterone play an important role in the retention of minerals in the kidneys (especially sodium), and in maintaining the potassium-sodium balance.

3. Describe the cells of islets of Langerhans and what hormones are secreted by them? What are their major functions, respectively?

The cells of islets of Langerhans produce insulin. Five different types of islets of Langerhans: alpha cells, which produce glucagon; beta cells, which produce insulin; delta cells, which produce somatostatins; and two other types of cells (PP and D1 cells), both of which produce human pancreatic polypeptide hormone, but whose precise functions are less well understood than those of alpha, beta, and delta islets of Langerhans cells. Alpha cell functions increase glucose production, while delta islets of Langerhan cell functions are inhibitory and regulate the production of other hormones.

4. Describe five methods currently used for diagnosis and monitoring of diabetes mellitus; and one of them is to test glycosylated hemoglobin HbA1C.

Diabetes mellitus is typically diagnosed and monitored through fasting plasma glucose levels, non-fasting plasma glucose levels, the presence of hyperglycemia, glycosylated hemoglobin (HbA1C), and diabetic ketoacidosis. Generally, fasting plasma glucose levels of 100-125 mg/dL, non-fasting glucose levels above 140 mg/dL, and glycosylated hemoglobin levels above 6% are considered to be glucose intolerant. Additionally, numerous cardiac, circulatory, immune system, ocular, and wound-healing issues are associated with diabetes mellitus and often precipitate its diagnosis.

5. Describe the characteristic of functional syncytium in the intestine.

Peristaltic contractions of consecutive intestinal segments creates and maintains forward movement of the bolus through the intestine. Segmental contractions also occur, which do not result in forward movement but are necessary to ensure thorough mixing of the bolus and maximal contact with the intestinal walls to facilitate optimal nutrient absorption.

6. Describe "LAW OF THE GUT" associated with gastrointestinal system

According to the Law of the Gut, gastrointestinal motility (peristalsis) consists of a rhythmic wave of contractions of smooth muscle fibers throughout the entire length of the digestive system that begins in the oral cavity and continues all the way to the anal sphincter.

7. What is the function of ileocecal valve?

The ileocecal valve is a sphincter that separates the small and large intestines. Its primary function is to prevent the reflux of the contents of the colon back into the small intestine.

8. Describe the gastrointestinal equality theory.

According to the gastrointestinal equality theory, nutrient absorption occurs at the same rate per unit section of the entire length of each respective portion of the small intestine. Likewise, fluid absorption occurs at the same rate per unit section of the entire length of the large intestine.

9. Physiologically, how does the body prevent food or acid reflux from the stomach?

The relatively sharp angle of connection between the esophagus and the stomach creates a natural valve that prevents food and acid reflux from irritating or damaging the esophagus. Additionally, the production of HCL in the stomach during the digestive process serves a dual role: it breaks down food in the stomach but also triggers the opening of the duodenum to allow the stomach contents to spill into the small intestine.

10. Describe LaPlace's law associated with gastrointestinal system and list two examples of diseases involving this law.

According to the Law of Laplace, within any pliable tube such as the walls of the intestine, the least amount of pressure is necessary to stretch the section with the largest diameter. Therefore, in cases unrelated to ileocecal valve malfunction, large distal bowel obstruction is a direct function of LaPlace's Law at the area of the cecum. For the same mechanical reason, the most frequent location of colonic perforation is also at the cecum because it is the area of the largest diameter, and therefore, most susceptible to rupture in comparison to areas smaller in diameter.

11. What are the major types of movement of small intestine?

The first major type of movement in the small intestine is peristalsis. The second major type of movement in the small intestine are discrete clustered contractions, which are comparatively small movements. The third type of major movement in the small intestine is giant migrating contractions, which are larger versions of peristaltic contractions believed to serve a bacterial cleansing purpose.

12. Describe gastric acid feedback function

Gastric acid feedback is controlled by nerve endings in the stomach that are sensitive to acetylcholine and gastrin-release peptide. Gastrin and acetylcholine both stimulate the production of gastrin. High levels of gastrin trigger the release of somatostatin and histamines, both of which then inhibit further release of gastrin through their effects on the parietal cells.

13. Describe trypsin, lipase, and amylase biological function

Trypsin released into the duodenum is important for the breakdown of peptides through hydrolyses. By breaking down proteins into their constituent amino acids, trypsin facilitates the absorption of sufficiently small molecules to pass through the membranes of the small intestine. Lipase is a digestive enzyme produced by the pancreas and is essential to the breakdown of lipids into fatty acids. During the digestion of lipids, lipase breaks the complex bonds of triglycerides into less complex monoglycerides for absorption. The enzyme amylase breaks down sugars and starches in the process of converting them into glucose for storage in the liver and the skeletal muscles. This process begins with the amylase within saliva in the mouth and continues in the intestines through amylase produced by the pancreas.

14. What hormones control gastrointestinal motility?

The hormones that control gastrointestinal motility are gastrin, secretin, and cholecystokinin.

15. Describe stomach nervous myenteric plexus, what condition will occur if it is dysfunctional?

Stomach nervous myenteric plexus is a component of the enteric nervous system that originates in the medulla oblongata and the vagus nerve. It is responsive to both sympathetic and parasympathetic impulses and is crucial for normal regulation of intestinal motility. Disruption in the impulses carried by the stomach nervous myenteric plexus results in severe impairment of intestinal motility and can cause chronic intestinal pseudo-obstruction.