Describe the three layers of meninges covering the brain.

Brain is covered with three meninges namely dura mater, arachnoid mater and pia mater. The tough dura mater, avascular arachnoid mater and delicate pia mater together protect the brain from any injury.

Explanation:

The three layers of meninges covering the brain are dura mater, arachnoid mater and pia mater.  

Dura mater: The outer most meninx of the brain is called dura mater. It is a tough and fibrous covering of the brain. Dura mater is made of dense irregular connective tissue and is continuous with epineurium.  

Arachnoid mater: The middle meninx present between pia mater and dura mater is the arachnoid mater. Arachnoid mater is avascular layer and is rich in collagen and elastic fibers.  

Pia mater: The deepest meninx is called pia mater. It is the delicate layer of connective tissue. Pia mater is rich in the blood vessels that deliver nutrients and oxygen to the spinal cord.

the abdomen (less formally called the belly, stomach, tummy or midriff) constitutes the part of the body between the thorax (chest) and pelvis, in humans and in other vertebrates. the region occupied by the abdomen is termed the abdominal cavity. the stomach secretes acid and enzymes that digest food. ridges of muscle tissue called rugae line the stomach. the stomach muscles contract periodically, churning food to enhance digestion. the pyloric sphincter is a muscular valve that opens to allow food to pass from the stomach to the small intestine.

"menstrual cycle is a complex cycle that consists of several processes. order of occurrence of steps in menstrual cycle are as follows:

1. high progesterone levels maintain the endometrium lining of the uterus.

2. endometrium lining breaks down and low levels of estrogen stimulate the pituitary to release fsh and lh.

3. fsh and lh stimulates the follicles to develop and the oocyte to produce estrogen.

4. rising estrogen levels suppress fsh production and development of other follicles.

5. a spike in lh causes follicle to rupture.

6. a breakdown of corpus luteum causes progesterone level to drop."