BIO 004 · Human Anatomy
Endocrine Anatomy
Endocrine Anatomy
A reference for the endocrine anatomy video and lab. This page covers the endocrine glands, where each one sits in the body, and the gross anatomy of the pituitary, thyroid, parathyroid, adrenal, and pancreatic glands. Hormone action belongs to physiology and is not covered here.
How to use this sheet
Notes prints the full reference for review.
Study prints as a fill-in-the-blank worksheet to complete while you watch the video or read.
Quiz me is on-screen practice: type the term, or click Reveal to check yourself.
The tables and sequences respond to Study and Quiz too, with a Reveal button on each row.
- Name the major endocrine glands and locate each one in the body.
- Describe the gross anatomy of the pituitary gland and its connection to the hypothalamus.
- Identify the parts of the thyroid, parathyroid, adrenal, and pancreatic glands.
- Name organs that are not endocrine glands but still contain endocrine tissue.
Your pre-work
Work through these the evening before class. None of it is turned in. It is how you learn the material and build your spaced recall.
This is more than a checklist. Ticking these boxes is the start, not the finish. Committing this material to memory and being able to apply it takes considerable time and repeated effort. You are not done when the boxes are checked. Put in the real hours, and keep coming back for frequent recall and review until the material is genuinely yours.
The Endocrine System, an Overview
The endocrine system is a scattered set of glands and tissues that signal the body by releasing hormones into the blood. This page covers where those glands sit and how each one is built.
- Endocrine systemthe glands and tissues that release hormones into the blood to signal distant cells
- Hormonea chemical messenger released by an endocrine cell that travels in the blood to act on target cells
- Endocrine glanda ductless gland that secretes its product directly into the surrounding fluid and blood
- Exocrine glandby contrast, a gland that secretes through a duct onto a surface; not part of the endocrine system
- Target cella cell that carries the receptor for a given hormone and therefore responds to it
The Major Endocrine Glands
The pure endocrine glands do nothing but make hormones. They are spread from the brain to the pelvis. Compare them by where each one sits.
| Gland | Location | Note | Main secretions |
|---|---|---|---|
| Hypothalamus | the floor and walls of the third ventricle, in the diencephalon of the brain | links the nervous and endocrine systems and directs the pituitary | releasing and inhibiting hormones; makes ADH and oxytocin |
| Pituitary gland | in the sella turcica of the sphenoid bone, hanging below the hypothalamus | the small gland the hypothalamus controls | anterior: GH, TSH, ACTH, FSH, LH, prolactin; posterior: releases ADH and oxytocin |
| Pineal gland | the posterior roof of the third ventricle, in the brain | a small, cone-shaped gland of pinealocytes, often with calcified corpora arenacea (brain sand) | melatonin |
| Thyroid gland | the anterior neck, just below the larynx, wrapped around the trachea | the largest purely endocrine gland | thyroid hormone (T3, T4); calcitonin |
| Parathyroid glands | the posterior surface of the thyroid gland, usually four small glands | tiny glands embedded behind the thyroid | parathyroid hormone (PTH) |
| Thymus | the mediastinum, behind the sternum | large in childhood, shrinks after puberty | thymosins |
| Adrenal glands | one capping the superior pole of each kidney | also called the suprarenal glands | cortex: aldosterone, cortisol, androgens; medulla: epinephrine, norepinephrine |
| Pancreatic islets | scattered through the pancreas, behind the stomach | the endocrine portion of the pancreas | insulin, glucagon, somatostatin |
| Ovaries | the female pelvis, one on each side of the uterus | the female gonads | estrogen, progesterone |
| Testes | the scrotum | the male gonads | testosterone |
The Pituitary Gland
The pituitary gland, or hypophysis, is about the size of a pea. It sits in the sella turcica and hangs from the hypothalamus by a stalk. Its two lobes come from two different tissues.
- Hypophysisanother name for the pituitary gland
- Sella turcicathe saddle-shaped pocket of the sphenoid bone that cradles and protects the pituitary
- Infundibulumthe slender stalk that connects the pituitary to the hypothalamus above it
- Hypophyseal portal systemthe set of blood vessels that carries hypothalamic signals directly to the anterior lobe
- Adenohypophysis (anterior lobe, pars distalis)the glandular anterior lobe; on a slide its cells sort into acidophils (pink/red), basophils (blue/purple), and pale chromophobes
- Neurohypophysis (posterior lobe, pars nervosa)the neural posterior lobe, made of nerve fibers and supporting pituicytes
Compare the two lobes by the tissue they are made of and how each connects to the hypothalamus.
| Lobe | Other name | Tissue | Link to the hypothalamus |
|---|---|---|---|
| Anterior lobe | adenohypophysis | glandular epithelial tissue | the hypophyseal portal system, a set of blood vessels |
| Posterior lobe | neurohypophysis | nervous tissue, an extension of the hypothalamus itself | a tract of nerve fibers running down through the infundibulum |
The Thyroid and Parathyroid Glands
The thyroid gland sits across the front of the trachea, and the four small parathyroid glands are embedded in its back surface.
The thyroid gland
- Thyroid glandthe largest purely endocrine gland, two lateral lobes lying against the trachea below the larynx
- Isthmusthe bridge of thyroid tissue, crossing the front of the trachea, that connects the two lobes
- Thyroid folliclesthe microscopic hollow spheres that make up the gland
- Colloidthe protein-rich fluid stored in the center of each follicle
- Follicular cellsthe cells forming the wall of a follicle
- Parafollicular cellsalso called C cells, scattered between the follicles
The parathyroid glands
- Parathyroid glandsusually four small, round glands on the posterior surface of the thyroid lobes
- Chief cellsthe main hormone-producing cell of the parathyroid glands
- Oxyphil cellsthe larger, pink-staining cells scattered among the chief cells; their function is uncertain
The Adrenal Glands
An adrenal, or suprarenal, gland caps the top of each kidney. Each gland is really two glands in one: an outer cortex and an inner medulla, formed from different tissues.
- Adrenal cortexthe outer region and the bulk of the gland, glandular tissue arranged in three layered zones
- Adrenal medullathe inner core, modified nervous tissue that belongs to the sympathetic nervous system
- Chromaffin cellsthe modified sympathetic neurons of the medulla that secrete epinephrine and norepinephrine
The cortex is built in three zones. Follow them in order, from the surface inward.
- Zona glomerulosathe thin outer zone, just beneath the connective tissue capsule
- Zona fasciculatathe thick middle zone, the widest of the three, its cells in straight columns
- Zona reticularisthe inner zone, a branching network of cells against the medulla
The Pancreas and the Gonads
The pancreas and the gonads are mixed organs. Each does an endocrine job alongside another role, so only part of the organ is endocrine tissue.
- Pancreasa soft gland behind the stomach, both an exocrine and an endocrine organ
- Pancreatic isletsalso called the islets of Langerhans, the small clusters of endocrine cells scattered through the pancreas
- Aciniby contrast, the exocrine clusters of the pancreas that make digestive enzymes; not endocrine tissue
- Ovariesthe paired female gonads in the pelvis, endocrine glands as well as reproductive organs
- Testesthe paired male gonads in the scrotum, endocrine glands as well as reproductive organs
Organs with Endocrine Tissue
Beyond the pure endocrine glands, many organs whose main job is something else still carry pockets of endocrine cells. Compare them.
| Organ | Endocrine tissue it contains |
|---|---|
| Hypothalamus | neurosecretory cells; a neuroendocrine organ that controls the pituitary gland |
| Heart | hormone-producing cells in the wall of the atria |
| Kidneys | cells that release a hormone driving red blood cell production, plus an enzyme acting on blood pressure |
| Stomach and small intestine | scattered endocrine cells in the lining of the digestive tract |
| Liver | cells that contribute to a growth-related hormone and to blood pressure control |
| Skin | cells that begin the production of vitamin D, which acts as a hormone |
| Adipose tissue | fat cells that release a hormone signaling the body's energy stores |
| Placenta | a temporary organ of pregnancy that releases hormones supporting the pregnancy |
See also: Histology: The Four Tissue Types for endocrine and exocrine glandular epithelium, and Body Cavities and Regions for the mediastinum, where the thymus sits.
Study questions
Work on answering these in writing, in your own words. They are the questions to bring to class, and good practice for the reasoning the exams ask for.
- Compare an endocrine and an exocrine gland by how each delivers its product.
- Name the major endocrine glands and one hormone associated with each.
- Explain the hypothalamus-to-pituitary relationship and why the pituitary is called the master gland.
- Compare the anterior and posterior pituitary by how each releases its hormones.
Step 2 . Retrieval check
Now explain it back, in your own words.
In 60 words or more, pull together what the video just taught you. Include the key concepts. This is the point where the learning actually sticks. After you submit, your spaced-recall cards for this topic unlock.