1. B
2. B
3. C
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The reproductive cycle in females is regulated primarily by HER HORMONES. Five hormones to be exact. These hormones are Estrogen, Progesterone, Luteinizing hormone (LH), follicle stimulating hormone (FSH), and gonadotropin releasing hormone.
Estrogen is from the ovaries. It helps regulate the menstrual cycle. It promotes the rapid growth of cell linings in the uterus to prepare for implantation resulting to pregnancy.
Progesterone is also from the ovaries. It is produced after ovulation and maintains the health of the lining within the uterus during pregnancy. If no pregnancy occurs, the progesterone level decrease and results to menses or monthly period.
Gonadotropin Releasing Hormone is secreted by the brain as a result of the hormonal changes that occur every month. It in turn stimulates the production of FSH and LH.
FSH stimulates the follicles inside the ovaries increase the amount of estrogen and progesterone produced in the first two weeks of the menstrual cycle.
The increase in estrogen level by FSH prompts the pituitary glands to release LH. Luteinizing hormone then signals the dominant follicle, made by FSH inside the ovaries, to release its eggs for possible fertilization.
Answer:
The three-chambered hearts of amphibians and nonbird reptiles are facultative, allowing variation in blood flow through the heart.
Explanation:
In Anatomy, cardiac cycle can be defined as a complete heartbeat of the human heart which comprises of sequential alternating contraction and relaxation of the atria and ventricles, therefore causing blood to flow unidirectionally (one direction) throughout the human body.
Generally, the cardiac cycle occurs in two (2) stages;
I. Diastole : in this stage, the ventricles is relaxed and would be filled with blood.
II. Systole: at this stage, the muscles contracts and thus, allow blood to be pushed through the atria.
All amphibians and reptiles except for crocodiles (having four-chambered heart) have three-chambered hearts, which typically comprises of a partially divided ventricle and two atria.
Hence, the correct statement about the three-chambered hearts of amphibians and nonbird reptiles is that, the three-chambered hearts of amphibians and nonbird reptiles are facultative, allowing variation in blood flow through the heart due to the partially divided ventricle.
