Endocrine System

Lab Overview

  • Review of endocrine glands discussed in class
  • Aim: to identify glands and understand hormones released

Class Structure

  • Frequency of classes: 3 times a week
  • Focus on reviewing endocrine system
  • Importance of identifying glands on models and slides

Gland Identification Objectives

  1. Identify glands on models:
    • Use mini torso and larger torso models.
    • Be able to identify glands correctly.
  2. Recognize glands on slides:
    • Especially the thyroid, pituitary, and pancreas.
  3. Know released hormones:
    • Identify hormones from different glands and their functions.

Overview of Endocrine Glands

  • Introduction to various glands:
    • Emphasis on recognizing variations in models from different manufacturers.
  • Main glands to identify:
    • Hypothalamus
    • Pituitary gland
    • Thyroid gland
    • Parathyroid gland
    • Adrenal glands
    • Pancreas
    • Thymus gland
    • Gonads (Ovaries and Testes)

Hypothalamus and Pituitary Gland

  • Hypothalamus:
    • Connection point between the nervous system and endocrine system.
    • Located just below the third ventricle.
    • Releases approximately 7 hormones (not required to memorize).
  • Pituitary Gland:
    • Located in the sella turcica.
    • Types:
      • Anterior Pituitary (Adenohypophysis)
      • Releases 6 hormones.
      • Posterior Pituitary (Neurohypophysis)
      • Stores 2 hormones made in the hypothalamus.

Hormones of the Anterior Pituitary

  1. Adrenocorticotropic Hormone (ACTH)

    • Stimulates adrenal cortex.
    • Function: Release hormones from the adrenal cortex.

  2. Thyroid Stimulating Hormone (TSH)

    • Stimulates thyroid gland to release hormones.

  3. Follicle Stimulating Hormone (FSH)

    • In males: Stimulates testes for sperm production (spermatogenesis).
    • In females: Stimulates ovaries for egg development (oogenesis).

  4. Luteinizing Hormone (LH)

    • In males: Stimulates testosterone production.
    • In females: Induces ovulation.

  5. Growth Hormone (GH)

    • Stimulates growth, elongation of long bones.

  6. Prolactin (PRL)

    • In females: Promotes milk production during pregnancy.
    • Role in premenstrual symptoms (PMS).

Hormones of the Posterior Pituitary

  1. Oxytocin (OT)

    • Functions in smooth muscle contraction (e.g., uterus during labor).
    • Works on a positive feedback loop (more hormone leads to more contractions).

  2. Antidiuretic Hormone (ADH)

    • Function: Water retention and absorption in kidneys.
    • Alcohol inhibits ADH, leading to increased urination.

Thyroid Gland

  • Identified as a butterfly-shaped structure.
  • Hormones released:
    1. Thyroid Hormones:
    • T3 (Triiodothyronine): More potent, increases metabolism.
    • T4 (Thyroxine): More abundant, converted to T3 when needed.
    1. Calcitonin:
    • Function: Lowers blood calcium levels by promoting bone calcium absorption.

Histology of the Thyroid Gland

  • On microscope slides:
    • Follicular Cells: Produce T3 and T4, surround the colloid.
    • Colloid: Stores T3 and T4 precursors.
    • Parafollicular Cells: Secrete calcitonin.

Parathyroid Gland

  • Typically 4 small glands located on thyroid's posterior surface.
  • Hormone Released:
    • Parathyroid Hormone (PTH):
    • Increases blood calcium levels, acts antagonistically to calcitonin.

Thymus Gland

  • Located anterior to the heart.
  • Hormone Released:
    • Thymosin:
    • Stimulates T-cell production for immune response.
  • Most prominent in childhood, atrophies with age.

Adrenal Glands

  • Located on top of kidneys (right and left adrenal).
  • Structure:
    • Cortex: two hormones - cortisol and aldosterone.
    • Medulla: two hormones - epinephrine and norepinephrine.

Hormones of the Adrenal Glands

  1. Cortisol:
    • Stress hormone; increases metabolic processes during stress.
  2. Aldosterone:
    • Regulates sodium and potassium levels in the body.
  3. Epinephrine (Adrenaline):
    • Initiates the fight-or-flight response.
  4. Norepinephrine:
    • Works in tandem with epinephrine during stress responses.

Pancreas

  • Structure: Includes head, body, tail, and ductal system for digestive secretions.
  • Endocrine Function:
    • Produces hormones through pancreatic islets.

Hormones of the Pancreas

  1. Alpha Cells:
    • Glucagon: Increases blood glucose levels.
  2. Beta Cells:
    • Insulin: Decreases blood glucose levels.
  3. Delta Cells:
    • Somatostatin: Regulates other hormone functions (e.g., TSH and GH).

Gonads

  1. Ovaries:

    • Hormones produced: estrogen and progesterone.
    • Function: Secondary sexual characteristics in females (breast development, menstrual cycle).

  2. Testes:

    • Hormone produced: testosterone.
    • Function: Secondary sexual characteristics in males (voice deepening, muscle development).

Closing Remarks

  • Review process: Check notes regularly (recommendation of 15 mins daily).
  • Prepare for quiz next week on today's topics.