The element necessary in the diet for proper thyroid function is

a) Megakaryoblast: The megakaryoblast is the precursor cell in the bone marrow that eventually becomes a megakaryocyte, which fragments to form platelets (thrombocytes).

b) Proerythroblast: This cell gives rise to red blood cells (erythrocytes), not platelets.

c) T lymphoblast: This is a precursor to T lymphocytes, part of the adaptive immune system.

d) Monoblast: This cell gives rise to monocytes, which become macrophages in tissues.

a) Hypothalamus: Oxytocin is synthesized by neurosecretory cells in the hypothalamus, specifically in the paraventricular and supraoptic nuclei. After production, it is transported down the axons of these neurons to the posterior pituitary gland, where it is stored and released into the bloodstream.

b) Somatic Nervous System: The somatic nervous system is part of the peripheral nervous system and controls voluntary skeletal muscle movements. It does not produce hormones and has no role in endocrine secretion.

c) Anterior Pituitary Gland: The anterior pituitary produces several hormones (like ACTH, GH, PRL, TSH, LH, and FSH), but oxytocin is not one of them. It is not produced by the anterior pituitary; instead, oxytocin is made in the hypothalamus and released from the posterior pituitary.

d) Posterior Pituitary Gland: While the posterior pituitary stores and releases oxytocin, it does not produce it. The production occurs in the hypothalamus, and the posterior pituitary acts as a storage and release site.