Glandular Tissue

Curriculum : Phase 1/Semester2/TOB /Session 4

2017/2018

Lecturer : Dr. Rajaa Ali Al- Taee

Msc. PhD. Histology G.mail: dr.rajaaali@gmail.com

Hammurabi Medical Collage / Babylon University

References:

• Histology Textbooks ‘Basic Histology’, Junqueira,13 th

Edition chapter 1,2,3.pp:1-72

• ‘Colour Atlas of Histology’ Gartner and Hiatt 5 th

Edition.

• http://www.histologyguide.com/

Glandular Tissue

Glandular Tissue

Objectives of the lecture:

1. Define a gland as an epithelial cell or aggregate of cells specialised for

secretion.

2. Classify glandular tissue, describing the meaning of the following

terms:

Exocrine or endocrine

Merocrine, apocrine or holocrine.

3. Describe the above mechanisms of secretion.

Glandular Tissue

4 . describe the mechanisms of endocytosis.

5. describe how endocytosis and secretion combine to give transepithelial transport.

6. explain the mechanism and importance of the glycosylation of newly synthesised

proteins in the Golgi apparatus.

7. describe the role of secretions in cell functions (e.g. in communication).

8. describe simple mechanisms of control of secretion (e.g. nervous, endocrine).

Glandular Tissue

Glandular Epithelium:

Glandular epithelium is more complex and varied than the epithelial

cells which cover surfaces or line tubules or vessels.

A gland is a single cell or a mass of epithelial cells adapted for

secretion.

Classification of Glands

• By destination

• By structure

• By nature of the secretion

• By the method of discharge

1. Exocrine glands

2. Endocrine glands:

• ductless glands

• Secretion

• Cells

By destination

Thyroid glandAdrenal gland

https://youtu.be/GUi84E6lUiY

Exocrine glands secrete into ducts or directly onto a free surface.

Their secretions include mucus, sweat, oil, ear wax and digestive

enzymes.

EXO = out side and crine = secret

Examples include :-

pancreas , stomach , sweat glands , salivary glands , mammary

glands , sebaceous glands , etc .

Endocrine glands - called “ductless glands” discharge their

secretions into the intracellular fluid, where it diffuses into the blood

stream. These secretions are hormones, or chemical messengers,

which regulate many body functions.

ee Examples include :-

Pituitary gland ,thyroid gland,adrenal gland,parathyroideees

exe

3. Mixed gland

(an exocrine and

endocrine gland)

The Pancreas.

Formation of glands from covering epithelia.

During fetal development epithelial cells proliferate and penetrate the

underlying connective tissue.

They may-or may not-maintain a connection with the surface

epithelium. When the connection is maintained, exocrine glands are

formed; with the connection lost, endocrine glands are formed.

Exocrine glands secrete to the body surface or gut via duct systems

formed from the epithelial connection.

Formation of glands from covering

epithelia.

The cells of endocrine glands, which secrete hormone) can be

arranged in cords or in follicles with lumens for storing the secretory

product.

From either the cords or follicles of endocrine cells, the secretory

product is released outside the cells and picked up by the blood

vessels for distribution throughout the body.

General structure of exocrine glands.

• Exocrine glands by definition have ducts that lead to an

organ or body surface.

• Inside the gland the duct runs through connecting septa and

branches repeatedly, until its smallest branches end in the

secretory portions of the gland.

Classification by

Structure

Secretory part: unicellular /

multicellular

acinar (alveolar) / tubular

coiled / branched *

Parotid gland: branched

Duct system:

1. Simple gland (single duct)

2. Complex gland (branched ducts)

Branching

ducts:

Main

↓

interlobular

↓

Intralobular

↓

Intercalary

Salivary gland

1-Exocrine glands:

Structural classification of exocrine glands:

1) unicellular glands

2) multicellular glands ↓

Goblet cell

Salivary gland

https://youtu.be/cdqLLa81-eE

Multicelular gland:

composed of :

1) An epithelial lined duct

2) A secretory unit called the acinus

3) Interstitial connective tissue

Classification by method of secretion:

Merocrine (exocytosis )

• secretion is released by exocytosis

of secretory granules (pancreas,

parotid gland, protein component

of milk from mammary gland).

Apocrine (pinch of )

• apical portion of cell along

with secretory product is

pinched off (lipid

component of milk from the

mammary gland).

Holocrine (rupture)

• entire cell is shed along with

secretory product (sebaceous

glands).

https://youtu.be/E5aJTpiwakI

• Classification by nature of secretion:

Ex: Salivary glands

• Classification by nature of

secretion:

mucous glands

Secretion: contains

mucopolysaccharides which collects in

the apical part of cell.

Cytoplasm: stain very lightly with H/E

stain

Nuclei: basally placed & flattened

(mucoid pushes the nuclei).

Secretion: thin, watery, rich in enzymes, protein in nature.

Cytoplasm: granular stain darkly & rich in rER.

Nuclei: rounded & basally placed.

serous glands

Sero-mucous gland

Mixed gland

muco-serous or mixed gland

Contain both serous & mucous secretory units.

Sometimes serous cells form crescentic caps on mucous acinicalled as serous demilunes.

According to above 4 criteria of classifications ,classify parotid

gland?

Endocytosis

• Engulfing

• Opposite of exocytosis

(merocrine secretion)

• Endo- & Exo-cytosis

(Transepithelial Transport)

https://www.youtube.com/watch?v=sBCDxPvu4F0&feature=youtu.be

Transepithelial Transport

• material endocytosed at one surface

• transport vesicle shuttles across cytoplasm

• material exocytosed at opposite surface

Golgi Apparatus:

Structure

Stack of disc-shaped cisternae

• One side of discs are flattened;

other concave

• Discs have swellings at their edges

• Distal swellings pinch off as

migratory Golgi Vacuoles

Golgy apparatushttps://youtu.be/3H5dSPQNlX8

Golgi Apparatus:

Function

• Packaging through condensation of contents

• Transport

• Adding sugars to proteins and lipids (Glycosylation)

Golgi Product Destinations

• Majority extruded in secretory vesicles

• Some retained for use in the cells (e.g. lysosomes)

• Some enters the plasma membrane (Glycocalyx)

Glycosylation & Specificity

• Branching sugars offer complex shapes for specific

interactions in the glycocalyx

• Destruction of this layer by enzymes alters many

specificity based properties of cells:

adhesion to substrates & neighboring cells

mobility of cells

communication with neighboring cells

contact inhibition of movement and division

Control of Secretion

• Nervous

• Endocrine control

• Neuro-endocrine control

• Negative feedback chemical mechanism

Q:Give one or more examples of glands for each type of above

controls?

Thank you for listen