Glandular Epithelia Overview

Glandular Epithelia

• Glandular epithelium is specialized epithelium with secretory function.
• It's typically cuboidal or columnar.
• It forms the secretory portion of glands, producing and secreting the glandular product.
• Glands can be single secretory cells (e.g., goblet cells) or groups of cells forming larger glands.
• Secretory cells synthesize, store, and release proteins, lipids, or carbohydrate-protein complexes.

Formation of Glandular Epithelium

• Gland formation begins during embryonic development.
• Epithelial cells form in connective tissue beneath existing epithelium.
• Initially, glands are connected to the surface epithelium via a duct.
• Later, glands differentiate into endocrine or exocrine types based on the presence or absence of ducts.

Exocrine Glands

• Secrete products into ducts leading to the surface epithelium.
• Classified by the number of cells: unicellular (e.g., goblet cells) or multicellular.
• Classified by shape: tubular or alveolar (acinar).
• Classified by duct structure: simple (single duct) or compound (branched ducts).
• Additional classification based on secretions: serous (watery), mucous (viscous), mixed (both serous and mucous).

Types of Exocrine Glands

• Simple tubular: single, unbranched duct, secretory portion is a tube
• Simple coiled tubular: single, unbranched duct, coiled secretory portion
• Simple branched tubular: single, branched duct, secretory portion is branched tubes
• Simple acinar: single, unbranched duct, sac-like secretory portion
• Simple branched acinar: single, branched duct, branched sac-like secretory portion
• Compound tubular: branched ducts, secretory portion is a tube
• Compound acinar: branched ducts, secretory portion is sac-like
• Compound tubuloalveolar: branched ducts, combined tubular and sac-like secretory portions

Modes of Secretion (Exocrine)

• Merocrine: secretions released through exocytosis (most common)
• Apocrine: secretions released with a portion of the cell's cytoplasm (e.g., mammary glands)
• Holocrine: secretions released with the entire cell's destruction (e.g., sebaceous glands)

Endocrine Glands

• Ductless glands secreting hormones directly into the bloodstream.
• Hormones have far-reaching effects, acting on target cells throughout the body.
• Hormone secretions are absorbed by thin-walled blood capillaries.

Types of Endocrine Glands (Histological Types)

• Trabecular: cells arranged in cords (e.g., adrenal glands, liver)
• Follicular: cells form spherical structures (e.g., thyroid glands)
• Disseminated: cells scattered in other tissues (e.g., Leydig cells in testes)

Hormone Types (Endocrine)

• Proteins/peptides (e.g., insulin, growth hormone)
• Lipid derivatives (steroids)
• Amino acid derivatives (e.g., epinephrine, thyroid hormones)

Hormone Effects

• Endocrine: hormones released into blood and act over long distances
• Paracrine: hormone diffuses a short distance and affects nearby cells
• Autocrine: hormones act on the same cell that produced them

Amphicrine Glands

• Exhibit both exocrine (ductal secretion) and endocrine (hormonal secretion) functions.
• Can be homotypic (same cells for both) or heterotypic (different cells for each). (e.g., pancreas)

Explore the specialized structure and function of glandular epithelia in this quiz. Learn about exocrine and endocrine glands, their formation, and the types of cells involved. Test your knowledge on how these glands play a crucial role in secretion and hormone production.