The answer is option b. lower esophageal sphincter.
Explanation:
As food enters the oropharynx swallowing reflex is initiated to bring about peristalsis (a wave-like motion), that conveys the food through the esophagus to the stomach. The esophagus is a tubular structure between the oral cavity and stomach. It has two sphincters that prevent retrograde movement of food. This includes the upper esophageal and lower esophageal sphincters.
The upper esophageal sphincter guards the entrance of the esophagus and is situated at the inferior end of the pharynx. This usually relaxes to allow food passage into the esophagus.
The lower esophageal sphincter also referred to as the cardiac sphincter is located at the lower end of the esophagus, just at the junction between the esophagus and the stomach. This allows passage of food into the stomach and prevents back flow of food and acid secretions into the the esophagus.
The correct option is b. lower esophageal sphincter
Explanation:
The esophagus is the initial part of the digestive tract and its function is the transport of the alimentary bolus from the pharynx to the stomach, through the thorax and avoid the reflux thereof. It begins and ends in two sphincter structures, the upper esophageal sphincter and the lower esophageal sphincter, which separate it from the pharynx and stomach. The lower esophageal sphincter has two functions: relax during swallowing and prevent reflux of the gastric contents into the esophagus in the postdeglutory period. After swallowing, there is a relaxation of the lower esophageal sphincter, pressure dropping to levels similar to those of the gastric fundus, which allows the bolus to enter the stomach. This relaxation lasts a few seconds and is followed by a strong contraction that prevents backflow of food.
A glomerulus is formed from the afferent blood vessels, a branch from the renal artery. The afferent arteriole collects blood from the glomerulus and extends to the renal tubule where it divides into capillaries that ramify the tubule. The afferent arteriole is wider than the efferent arteriole.
