Glands Thyroid Gland: An endocrine gland IH SA

Glands Thyroid Gland: An endocrine gland IH SA

Glands Thyroid Gland: An endocrine gland IH SA N A gland is a cell or an organ that secretes substances for use inside or outside the body. An exocrine gland R Composed predominantly of epithelial tissue F. D

Classified as: PR O Endocrine Exocrine Mixed Stomach: Both an exocrine and an endocrine gland Exocrine Glands IH SA N Produce secretions: F.

D R Onto epithelial surfaces PR O Through ducts Exocrine Glands Exo = outside and crine = secrete. IH SA N Secrete material into ducts that lead to body surface or cavities, e.g., digestive, respiratory tract.

The parotid gland (a salivary gland) PR O F. D R Can be multicellular or unicellular. Multicellular: Pancreas, stomach, sweat glands, salivary glands, etc. Unicellular: Goblet cells. Goblet Cell Endocrine Glands N Release hormones:

PR O F. D R No ducts IH SA Into interstitial fluid Endocrine Glands Endo = within. N Do not secrete material into ducts.

F. D R IH SA Secrete their products into C. tissue blood stream where they travel through the body and affect other cells. Examples PR O Thyroid, thymus, testes, ovaries, pituitary, pineal, adrenal, etc. PR

O F. D R IH SA N Glands development IH SA N Glands are derived from epithelia, which form a down-growth into the underlying connective tissue. PR O

F. D R Cells then develop into mature gland. Exocrine glands maintain connection with body surface whereas it is lost by endocrine glands. Epithelium Cell differentiation, & proliferation Mesenchyme IH SA

N Mesenchymal-epithelial exchange of signals PR O F. D R GLAND DEVELOPMENT Construction of lumens Stroma Differentiation into duct & secretory cells Simple alveolar gland Epithelial downgrowth

into modified mesenchyme PR O F. D R IH SA N Mechanisms of Glandular Secretion Holocrine Merocrine Apocrine

(whole cells) (vesicles) (cell parts) Modes of Secretion Merocrine:( Eccrine) IH SA N Membrane bounded vesicles open onto the surface of cell, PR O F.

D R Secretory product is discharged through exocytosis without any further loss of cell substance, e.g. sweat glands, salivary glands R IH SA N Modes of Secretion F. D

Apocrine: Part of apical cytoplasm is lost together with secretory product. PR O Plasma membrane is repaired by fusion of broken edges of the membrane, cell is able to accumulate new secretory product, e.g. apocrine sweat glands, mammary glands, prostate. Apocrine glands are really merocrine glands but confusing appearance (apical cytoplasm not lost as used to be believed) PR O F. D R IH SA

N Modes of Secretion Holocrine: Breakdown and discharge of entire secretory cell. Secretions released by cells bursting, killing gland cells, replaced by stem cells, only seen in sebaceous glands of skin. PR O F. D R IH SA N Glands Histological Structure of Large Exocrine Glands Parenchyma secretory tissue;

Stroma supporting connective tissue. IH SA N Capsule. layer of dense irregular connective tissue R Septa C. tissue sheets extend from capsule; subdivide the gland into a number of lobes. F. D Thinner c. tissue septa subdivide the lobes into a number of lobules. PR O

Reticular connective tissue surrounds and supports secretory units of glands (alveoli, acini etc.) and the initial parts of the excretory ducts if present. Blood, lymph vessels, nerves penetrate the capsule and form a delicate network between the secretory units. PR O F. D R IH SA N Glands N Main excretory duct conveys secretory product out of the gland. Other parts of duct system are named according to their relation to lobes and lobules of the gland.

IH SA Interlobar ducts are found in the connective tissue surrounding the lobes. R Lobar ducts extend to lobes of the gland. PR O F. D Interlobular ducts, are found in c, tissue surrounding lobules of the gland. Lobular ducts. branches of duct system to lobules, Intercalated ducts. Terminal branches which connect lobular ducts with secretory units of the gland PANCREAS

Exocrine acini PR O } F. D R IH SA N Duodenal papilla Endocrine portion Principal duct

Interlobular duct Intralobular ducts Lobule Intercalated ducts PR O F. D R IH SA N Interlobular duct Classification of Exocrine

Glands IH SA N Exocrine glands may be classified according to; Unicellular PR O F. D R 1. Cell number, Multicellular

2. Shape and branching pattern of their secretory portions and ducts. Unicellular Glands IH SA N Consist of a single secretory cell. e.g. goblet cells, in epithelium of mucous membranes. F. D R A modified columnar cell PR

O Goblet cells secrete glycoprotein mucin, which by uptake of water is converted into a slimy substance, mucous. PR O F. D R IH SA N PR O F. D

R IH SA N Unicellular Gland Goblet cell PR O F. D R IH SA N Multicellular glands F.

D R IH SA N Its simplest form is a surface epithelium consisting entirely of secretory cells (e.g. stomach, where mucous secretion protects stomach wall from acidic contents of the stomach). PR O Other multicellular glands have their secretory portion embedded in c.

tissue underlying the epithelium. PR O F. D R IH SA N Classification on the basis of shape and branching pattern of secretory portions and ducts. PR O F. D R

IH SA N Simple exocrine glands Single duct Compound exocrine gland Branching duct system PR O F. D R IH SA N

Types of simple exocrine glands PR O F. D R IH SA N Types of compound exocrine glands Types of Secretions On the basis of types of secretion three types IH SA

N Serous glands: watery secretions F. D R Mucous glands: secrete mucins PR O Mixed glands: both serous and mucous MUCOUS TUBULE IH


PR O F. D R IH SA N Based on Product(s) released (serous, mucous, mixed) Sublingual Parotid Submandibular GLANDULAR EPITHELIA: Products & Roles Airway glands, Salivary glands

Extra defense Airway glands Digestion Gastric glands, Pancreas N Extra mucus Liver Hormones Endocrine glands F. D Milk

R IH SA Blood processing Mammary glands Sweat glands Grease Sebaceous glands PR O Sweat Special genito-urinary functions

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