Glands Histology lab 5 Notes by Lojayn Salah

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1 Glands Histology lab 5 Notes by Lojayn Salah There are two types of glands: - 1) Endocrine gland: collection of epithelial cells with no connection with the epithelial surface, it has no duct, its secretory products (hormones) directly go to the blood circulation. 2) Exocrine glands: collection of epithelial cells, they have connection through ducts to the surface epithelial, such as * Lacrimal glands: are tear producing glands * Sweat glands: sweat producing glands Classifications of the glands: First Classification: according to the number of the cells in the gland: a) Unicellular Gland: it is composed of one cell only, example: (Goblet cells; mucus secreting cells) Goblet Cell: modified epithelial cell, columnar cell, it s wide apically and narrow basally, organelles and nucleus are concentrated in the basal part of the cell, while the apical part of the cell contains secretory granules( the secretory granules contain mucin not mucus) Mucins are glycosylated proteins, one it s released from the cell, it mixes with water (mucins become hydrated, here we call it mucus). Accordingly, Do you think we can see these secretory granules using hematoxylin and eosin?

2 No, because they cannot stain glycosylated proteins, so in order to see these granules we need to use PAS stain - specific for carbohydrates rich structures-. 2 Examples where you could find goblet cells: 1) Respiratory Epithelia: Goblet cells looks empty, unstained and bubbled shape appearance. 2) Lining of intestine: for protection. b) Multicellular Gland: have more than one cell, example: (all of the exocrine glands are multicellular glands, like salivary glands which secretes saliva )اللعاب( into the oral cavity into the mouth-. - The simplest form of gland is composed of: 1) single duct (lined with ductal cells: which are passive cells, do not do anything except passing secretory products to reach the surface of the epithelia, usually they are execratory. Notice that the color of the ductal cell is the same as the surface of the epithelia. 2) Single secretory unit: cells specialized for secretion. We said that the classification of exocrine glands is according to: a) Duct Morphology; One single Unbranched Duct Simple Gland,, More than one branching Duct Compound Gland ** According to Duct Morphology we determine the first part of the glands name. b) Shape pf secretory units; Ball structure Acinar (alveolar),, Tube like structure Tubular. * Some glands have tube like and acinai shape, so we call it Tubulo- Acinar. - Single Duct, One tubular secretory unit Simple Tubular. - Single Duct, more than one tubular secretory unit Simple Branched Tubular.

3 ** Branched describes the secretory unit not the duct> ** Once we have used simple, it means single duct not branching duct. - Single Duct, One Ball shaped secretory unit Simple Acinar / Simple Alveolar. - Single Duct, more than one Ball shaped secretory unit Simple Branched Acinar / Simple Branched Alveolar. - Compound Duct, tube like Secretory unit Compound Tubular. ** Why we don t say Compound Branched Tubular? Because if it is by default is compound, so for sure I have more than one secretory unit. - Compound Duct, Ball Shaped Secretory portion Compound Acinar / Compound Alveolar. - Compound Duct, Tube and Ball Shaped Secretory portion Compound Tubulo-Acinar / Compound Tubulo-Alveolar. ** According to the plane of your section of the parts may not appear ( in the exam the long access of the whole gland will be clear Examples about Simple Glands: 1) Simple Coiled Tubular: How Simple Coiled Tubular appear in the histological section? Circular profile with lightly stained areas (secretory portions) and darkly stained areas (Ducts). Important Sweat Gland is Simple Coiled Tubular. - We don t have to know where we can find the Simple Branched Tubular Gland, but we need to identify it one duct with 2\3 branched secretory units. 2) Simple Branched Acinar:

4 Hair have two parts: a) Visible Part (Above the level of the skin), b) Embedded part (Within the skin). The structure where the hair is inside the skin is called Hair Canal. Simple Branched Acinar Gland is the type of glands within hair canal, this gland called: Sebaceous gland, it secretes sebum into the hair canal which is oily material or lipid, in order to lubricate the hair and the surface of the skin. * People with oily skin have excessive of this type of glands. How it appears in the histological section? First we see the skin, the hair is missed during preparation, single duct below the hair canal with branched secretory portions (ball shaped), and usually the duct may not appear, secretory cells are lightly stains (they produce lipids so they are not stained with hematoxylin and eosin), secretory cells are small in shape and the nucleus is in the middle. * We need to know that Sebaceous Glands are Simple Branched Acinar Glands. * NOTE: when you take sections through acinai like structure you will see circles with no lumen, except if you take it from the center you will see small lumen. But if you take sections through tube like structure in all cases you will see lumen, but it may not appear always as circles. Classifications of glands according to the nature of secretory product: 1) Some glands secrete mucous material (which is viscus material, rich in glycosylated proteins) - This type of glands is lightly stained (remember goblet cells), it s not stained with H&E. - Usually Mucous Secretory Glands arranged in tube like structure (empty, bubbled shape). 2) Other Glands secrete serous (Watery secretion, fluid, rich in enzymatic activity)

5 - The Basal part of this type of Glands is basophilic because it has prominent RER and nucleus, so it s darkly stained, and the Secretory Vesicles are Acidophilic. - Serous Secretory Cells usually arranged into Acinai like structure. 3) Gland secrete Mucous and serous (mix glands). tubule-acinair ** When you want to identify any cell you have to ask yourself two important questions: 1) is it simple/compound? 2) Secretes Serous/Mucous? If you remember we ve talked about 3 types of Salivary Glands: 1) Inside the ear: Parotid Gland. 2) Below the tongue: Sublingual Gland. 3) Below mandibular: Submandibular Gland. you have to memorize 2 Example for about the Compound Acinar (Both start with p ) 1) Parotid 2) Pancreas ** Both Sublingual and Submandibular Glands are mixed glands زGlands Compound Tubulo-Acinar ** Parotid Gland Secretes Serous, so it is Compound Acinar Gland. ** Saliva has serous and mucus secretion (mixed). ** Pancreas is (endocrine and exocrine gland): Secreting insulin to blood circulation ( no duct) is the endocrine part on pancreas. Secreting pancreatic enzymes and digestive enzymes through a duct to small intestine is the exocrine part of pancreas. Classifications Of Glands according to the mode of secretion: 1) Merocrine glands. 2) Apocrine glands.

6 3) Holocrine glands. Clinical application (very important): At puberty time, there is excessive secretion of sexual hormones in both genders, these sexual hormones effect Sebaceous Cells, the hormones stimulate secretion from these glands, this will cause blockage of the duct, because of the excessive secretion, so the sebum will concentrate below the skin and give acne الشباب( )حب, the inflammation is because of the bacteria, same concept for black heads. Types of sweat Glands: 1) Simple Coiled Tubular with duct open to the surface of skin this gives typical sweat (water + salt) Merocrine mode of secretion all of the body. 2) Simple Coiled Tubular with duct open to the hair canal rather than the skin secretion of sweat associated with hair in certain areas like axilla and armpit Apocrine mode of secretion it has wide lumen. Important notes about glands: More serous secretion seromucous glands ex. submandibular gland More mucous secretion mucoserous gland ex. Sublingual gland فرسان النهضة كنا جيلا بالهمة نكبر