the tunica media consists almost entirely of smooth muscle why?
The Ciliary Muscle is a circular ring of smooth muscle attached to the lens of the suspensory ligaments.
Yes, there are two anal sphincter muscles: the internal anal sphincter, which is made of smooth muscle and is under involuntary control, and the external anal sphincter, which is made of skeletal muscle and is under voluntary control.
It is a doughnut-shaped ring of smooth muscle that opens to allow chyme from the stomach to enter the duodenum.Read more: What_is_the_structure_of_the_pyloric_sphincter
Smooth muscles make up most of the esophagus, but the upper portion also contains some voluntary or skeletal muscle. The muscles move in a wave like pattern to move food down into the stomach through a process called "peristalsis". At the distal end is the lower esophageal sphincter, a ring of smooth muscle that controls movement of food between the stomach and esophagus.
Carotid arteries supply blood to brain . Blood is supplied to the entire brain by 2 pairs of arteries: the internal carotid arteries and vertebral arteries. The right and left vertebral arteries come together at the base of the brain to form a single basilar artery. The basilar artery joins the blood supply of the internal carotid arteries in a ring at the base of the brain. This ring of arteries is called the circle of Willis. The circle of Willis provides a safety mechanism...if one of the arteries gets blocked, the "circle" will still provide the brain with blood.
The cervix, or cervix uteri, is the ring of muscle found at the base of the uterus.
The valve preventing the movement of chyme from the duodenum into the stomach is called the pyloric valve. The pyloric valve consists of a ring of smooth muscle and is connected to the duodenum.
It's from a Latin word meaning "ring" because it's a ring of muscle.
The Iris.
The color ring of muscle that controls the size of the pupil is called the iris. It can expand or contract to regulate the amount of light entering the eye.
papilla constrictor muscle of iris diaphragm
The ring like muscle that controls the flow from the stomach to the small intestine is called the pylorus or the pyloric sphincter. It is divided into two parts: the pyloric antrum which is connected to the body of the stomach and the pyloric canal which is connected to the beginning of the small intestine (the duodenum).