Introduction Types of glands Classification Functions of glands GLANDULAR EPITHELIUM Introduction Types of glands Classification Functions of glands

Introduction: Glands are derivatives of surface epithelium. Cells from mother epithelium invaginate the connective tissue beneath then develop the gland If the connection between the two persists, exocrine gland forms. The connection is the duct of the gland If the connection obliterates, endocrine gland forms.

TYPES OF GLANDS (Classification) There are the following groups: Exocrine glands: Pass secretions through a duct system to a body surface Secretions are normally enzymes 2. Endocrine glands: Pass secretion directly into blood or lymph (internal secretion) Secretions are normally hormones 3. Mixed glands: These have both exocrine and endocrine components.

Types of Exocrine glands a. According to the number of secreting cells unicellular glands – a single cell is a complete gland. Good example is a Goblet cell (mucous cell). Multicellular glands – each gland is formed by more than one cell, examples are Parotid (salivary) glands and Pancreas.

Holocrine. whole cell dies, the discharges go Exocrine gland b. According to the mode of secretion Holocrine. whole cell dies, the discharges go together with the cellular contents (remnants of a dead cell) eg. sebaceous and tarsal gland cells.

Apocrine. (membrane budding) Products Exocrine gland Apocrine. (membrane budding) Products accumulate at the apical part of the cell then discharges its apical cytoplasm eg mammary gland cells.

Merocrine. Only cell products are discharged Exocrine gland Merocrine. Only cell products are discharged eg sweat gland cells. Cytogenous. A product is a complete living cell. eg gonads (testes and ovaries)

Simple glands. All cells discharge to single duct Types cont………. c. According to the shape of secreting units: Simple glands. All cells discharge to single duct tubular – tube like unit. May be straight or coiled tails. saccular/alveolar/acinus – pocket like unit simple tubular straight / coiled

Compound glands. Several single units share a common discharging duct. Types cont………. Compound glands. Several single units share a common discharging duct. compound tubular Compound saccular/alveolar Compound tubulo-alveolar Compound saccular

Compound glands

EXOCRINE GLANDS SIMPLE COMPOUND TUBULAR SACCULAR Or ALVEOLAR TUBULAR Secreting units….. . EXOCRINE GLANDS SIMPLE COMPOUND TUBULAR SACCULAR Or ALVEOLAR TUBULAR SACCULAR Or ALVEOLAR TUBULOALVEORAL TUBULAR coiled TUBULAR straight

d. According to the nature of secretions: Types cont………. d. According to the nature of secretions: Serous glands. Waterly secretions Mucous glands. Mucoid or mucin secretions Seromucous glands. Mixed serous and mucous secretions

Endocrine glands cells). Unicellular - (rare-known. example – enteroendocrine cells). Multicellular with the cells surrounded by the conn. Tissue capsule sending inward septae into unit structures. TYPES are: a. According to the cell arrangement (grouping): i. cord and clump gland – cells are arranged like a bunch of grapes. ii. Follicle gland - cells are circularly arranged with a central lumen. iii. Scattered masses – aggregated cells housed in an organ . .

b. According to secretion storage site: Endocrine…… b. According to secretion storage site: i. intracellular – secretions are stored inside the cell prior discharge. ii. Extracellular – secretions are stored outside the cell prior discharge

Functions of glands ( Exocrine/endocrine) 1. Secretion. Exocrine glands secret watery and enzyme components. Endocrine glands secret hormones. 2. Storage of secretory materials. 3. Protection. 4. Absorption.