Endocrine and Exocrine Glands

Brown adipocytes contain numerous smaller droplets and a much higher number of mitochondria, which make them brown. They are abundant in newborns and hibernating mammals.

The thymus gland is crucial for the immune system as it's where T-lymphocytes mature and differentiate. It produces lymphocytes and is involved in antibody production. The hypothalamus regulates hormones, adrenals produce adrenaline and cortisol, and thyroid regulates metabolism.

Gull's disease results from thyroid dysfunction, causing myxedema with characteristic skin swelling and mental slowing. The thyroid gland regulates metabolism through hormone secretion, and its failure produces these symptoms. Other endocrine glands (pituitary, adrenal cortex, gonads) cause distinct disorders when dysfunctional.

The pineal gland secretes melatonin, the hormone that regulates circadian rhythms (sleep-wake cycles), earning it the name 'biological clock'. Melatonin production increases in darkness and decreases in light, synchronising our internal body clock with the external day-night cycle. The adrenal gland secretes cortisol and catecholamines (stress response), pituitary is the 'master gland' controlling other endocrine glands, and thyroid regulates metabolism - none are the biological clock.

The pancreas produces insulin in special cells called beta cells of the islets of Langerhans. Insulin regulates blood sugar levels. The pituitary gland is the 'master gland' that controls other glands, pineal regulates sleep cycles, and adrenal produces stress hormones like cortisol.

The pituitary gland is called the 'master gland' because it controls other endocrine glands through hormone secretion. Pineal regulates sleep, adrenal produces stress hormones, and pancreas produces insulin - but they're controlled by pituitary signals.

Endocrine glands are glands that secrete their products, mainly hormones, directly into the blood. Tropic hormones are hormones that have other endocrine glands as their target.

Addison's disease is caused by adrenal cortex insufficiency, leading to decreased production of cortisol and aldosterone hormones. The adrenal medulla secretes adrenaline and noradrenaline, while pituitary and thyroid are distinct endocrine glands.

Wharton's duct is the main excretory duct of the submandibular salivary gland, located on the floor of the mouth beneath the tongue. It drains saliva from the submandibular gland into the oral cavity.

Dysfunction of Meibomian glands causes dry eyes.

Thymus provides an environment for development of T-cells from hematopoietic progenitor cells. 

Rathke's pouch gives rise to the anterior pituitary (adenohypophysis) part of the pituitary gland.

Nest-like bodies called Hassall's corpuscles are found in thymus gland. 

Fenestrated capillaries allow small molecules and limited amounts of protein to diffuse and are present in the endocrine glands.