A group of ductless glands that secrete hormones directly into the blood stream.
They are:
1- Pituitary gland: A small gland 1/2 gm in weight which lies in a special fossa in
the middle part of the base of the skull, below the brain. It secretes many
hormones which circulate in the blood and control the secretion of all the
remaining endocrine glands, as TSH, ACTH, prolactine hormone and growth
hormone.
2- Thyroid gland: Butterfly gland which lies in front of the lower part of larynx and
upper part of trachea in the lower part of the neck. It consists of 2 pyramidal-
shaped lobes which are connected together by a transverse band called isthmus.
It moves up and down with the movement of larynx during swallowing. It
secretes thyroxin hormone.
3- Parathyroid glands: 4 small yellowish glands embedded in the posterior surface
of the thyroid gland and responsible for secretion of parathyroid hormone (PTH)
which regulates the calcium and phosphorus metabolism.
4- Suprarenal glands (Adrenals): Two semilunar or triangular glands present at
the upper poles of the kidneys. Each gland has cortex and medulla, the cortex
secretes cortisone and aldosterone hormones while the medulla secretes
adrenaline and noradrenaline hormones.
5- Pancreas: A mixed endocrine and exocrine gland which lies transversely on the
posterior abdominal wall extending from the duodenum till the spleen.
Its endocrine part is called islets of Langerhans, which secretes insulin and
glucagon hormones that regulate the blood glucose level.
6- Gonads: Two testes in male and two ovaries in female:
a- Testis in male secretes testosterone hormone.
b- Ovary in female secretes oestrogen and progesterone hormones.