Chapter 13 - Endocrine Glands

The endocrine system is created of glands that synthesize and secrete products, called hormones, directly into the blood fairly than with a duct. Hormones space transported transparent the body where they affect only those cells that have receptors for the hormone.

You are watching: Which type of gland secretes directly into tissue fluids and the blood without ducts?

Hormones have the right to be:

Proteins/peptides (e.g., insulin, development hormone) Lipid derivatives - derived from cholesterol or fat acids (e.g., steroids, eicosanoids) Amino acid derivatives - derived from tyrosine or tryptophan (e.g., epinephrine, melatonin, thyroid hormones) Hormone results are described as: Endocrine - released right into blood and act at long distances Paracrine - diffuse a brief distance with tissue fluids to surrounding cells Autocrine - plot on the very same cell that developed the hormone

Endocrine glands are highly vascular and also often save fenestrated capillaries to facilitate the diffusion that hormones into blood.


The pituitary is often dubbed the "master gland" of the body because it produces hormones that regulate other endocrine glands, also as, have direct effects on target tissues.





The thyroid gland produces hormones, triiodothyronine (T3) and thyroxine (T4), that primarily affect the basal metabolic rate and protein synthesis.



Parathyroid glands secrete parathyroid hormone (PTH) in solution to low blood level of calcium. PTH secretion causes the relax of calcium from bones by stimulating osteoclasts, inhibition of osteoblasts, and also increased reabsorption of calcium in the kidney.


This specimen is unusual in that thyroid, parathyroid gland and also thymus failed to migrate to their suitable locations during development.

Adrenal Glands

Adrenal glands create a variety of hormone that aid regulate metabolism, blood pressure, response to stress, and other essential functions.

See more: What Is Mayo Made Of Dairy ? What Is In Mayonnaise Anyways? Is Mayo Dairy

Pancreatic Islets

Pancreatic islets (or islets of Langerhans) space "islands" that endocrine cells situated within the pancreas. They secrete hormones (insulin and also glucagon) necessary in the regulation the glucose in blood.