HistoReview_3rdShift.pdf

UST FACULTY OF MEDICINE AND SURGERY Class of 2016 o

Histology

Trapping of particulate matter: mucussecreting glands and cilia

Third Shifting Reviewer Nasopharynx RESPIRATORY SYSTEM Conducting System  Nasal cavity  paranasal sinuses  nasopharynx  trachea primary bronchi  secondary bronchi  terminal bronchioles  Contains mucus-secreting cells and cilia  For cleansing, warming, and conducting of air

 

Composed of respiratory epithelium o Patches of squamous epithelium increase with age Lamina propria rich in serous and mucous glands and large masses of lymphoid tissue called the adenoids or nasopharyngeal tonsil (part of Waldeyer’s Ring)

Gaseous Interchange System  Transitional airways (respiratory bronchiole)  alveolar duct/ sac  alveoli and pulmonary capillaries  From the terminal bronchioles, there is a series of “transitional airways”: respiratory bronchioles and alveolar ducts  For gas exchange

Larynx

Nasal Cavity

Ventricle  Narrow cleft between the true and false vocal cords composed of respiratory epithelium with seromucous glands  Terminates as a blind-ending saccule

  

 

Consists of external vestibule and internal nasal fossa Two nasal cavities divided by a cartilaginous nasal septum Function enhanced through enlarged surface area by turbinate system o Temperature regulation o Humidity o Trapping of particulate matter Olfactory mucosa at the roof of the nasal cavity which function as receptors for smell Conchae o Superior: olfactory epithelium  Mucous secreted by Bowman’s gland; no goblet cells  Has olfactory hair/ cilia which are receptor structures o Middle and Inferior: respiratory epithelium  With goblet cells

Nasal Mucosa  

Composed of “respiratory epithelium”: pseudostratified columnar ciliated epithelium with goblet cells Lamina propria is rich in vessels and serous and mucous glands o Temperature of inspired air: adjusted by rich plexus of blood vessels and serous gland secretions

False Vocal Cord  Upper fold composed of respiratory epithelium True Vocal Cord  Lower fold composed of stratified squamous epithelium  Contains the vocalis muscle and vocalis ligament

Epiglottis  

Stratified squamous non-keratinizing epithelium Elastic cartilage that presents with degenerative fatty changes with aging

Trachea  

 



Flexible tube of fibro-elastic tissue and cartilage which permits expansion, extension, and recoil Composed of respiratory epithelium with the following components: o Tall pseudostratified ciliated columnar cells (more plentiful in lower trachea) o Goblet cells o Serous cells o Basal cells (neuroendocrine system) o Basal stem cells o Thick basement membrane Lamina Propria consists of loose and highly vascular connective tissue Submucosa contains seromucinous glands that decrease in number at the lower parts; merges with perichondrium of underlying hyaline cartilage rings C-Shaped Hyaline Cartilage Rings o Support tracheal mucosa and prevent its collapse

By: Sachi Estreller |Section B

1

UST FACULTY OF MEDICINE AND SURGERY Class of 2016 

Trachealis Muscle o Join free ends of the rings posteriorly o Contraction reduces tracheal diameter and assists in raising intrathoracic pressure during coughing

Primary Bronchus     

Respiratory epithelium is less tall and contains fewer goblet cells Lamina Propria is separated from submucosa by a layer of smooth muscle (smooth muscle more prominent) Submucosa contains fewer seromucinous glands Cartilage exist as flattened plates rather than distinct rings Has Bronchus Associated Lymphoid Tissue (BALT), component of diffuse MALT

Tertiary (Segmental) Bronchus     

Respiratory epithelium has little pseudostratification with greatly diminished goblet cell number Lamina Propria is thin, elastic, and completely encircled by smooth muscle disposed in a spiral manner Submucosa has sparce seromucinous glands Cartilage disposed to few irregular plates and does not extend beyond the tertiary bronchi MALT are present in the adventitia

Bronchiole 

 

Ciliated columnar epithelium with goblet cells o In the terminal and respiratory bronchioles, goblet cells are replaced by clara cells (tall columnar cells with apical secretory granules) < 1mm in diameter with no cartilage or submucosal gland components Smooth muscle and neuroendocrine cells are present

Terminal Part of the Respiratory Tree Terminal Bronchioles  Smallest diameter passages of purely conducting portion of respiratory tree  Further divide to form respiratory bronchioles Respiratory Bronchioles  Ciliated cuboidal epithelium with clara cells (no goblet cells) o Clara cells are non-ciliated cells that function to produce one component of surfactant, act as stem cells, and detoxify noxious substances

 

Contain few alveoli that start to function for gas exchange; alveoli increase in number Divide to form alveolar ducts

Alveolar Ducts  With numerous alveoli along their length  End in alveolar sacs which open into several alveoli  Smooth muscle component appear knob-like

Alveoli Surface Epithelium  Type I Pneumocytes (Small Alveolar Cells) o About 40% of epithelium o Large, squamous cells o Alveolar lining cells that is part of the thin gaseous diffusion barrier  Type II Pneumocytes (Great Alveolar Cells) o About 60% of epithelium o Rounded cells with large nuclei (dispersed chromatin and dispersed nucleoli) o Lamellar Bodies  Fine vacuoles in cytoplasm that contain phopholipid palmityl phosphatidylcholine)  Storage and release site of surfactant o Functions:  Secrete surfactant (tubular myelin) which serves to reduce surface tension, preventing alveolar collapse during expiration  Surfactant has aqueous hypophase and lipid monolayer  Retain capacity for cell division and can differentiate to Type I Pneumocytes as needed Supporting Tissue  Fine reticular, collagenous and elastic fibers with occasional fibroblasts  Elastin and septal collagen of the alveolar wall are continuous with those of adjacent alveoli  Alveolar septum o Composed of 3 laminar structures constituted by a central basement membrane and 2 very thin cytoplasmic layers o Septa contains small openings called alveolar pores of Kohn, which allow

By: Sachi Estreller |Section B

2

UST FACULTY OF MEDICINE AND SURGERY Class of 2016 movement of air between alveoli and also movement of pathogenic organisms Blood Vessels  Air-Blood Barrier o Type 1 pneumocyte + fused basement membrane + capillary endothelium o Basement membrane of the capillary endothelium is directly applied to basement membrane of surface epithelium, without interfering supporting tissue Alveolar Wall  Composed mainly of capillaries that form a basket-like arrangement around each alveolus  Type I pneumocytes are located on the convex side of the basement membrane  Surface endothelial cells located on the concave side of the basement membrane  Type II pneumocytes are located at the branching point of the alveolar septum

Small Pulmonary Vein  Amount of smooth muscle in tunica media increases progressively along venous network  With ill-formed elastic laminae

The Visceral Pleura   

Outer surface lined by a layer of flattened cuboidal mesothelium supported by thin basement membrane Mesothelial cells have plentiful long surface microvilli which trap hyaluronic acid that enhances the lubrication of the two surfaces Fibrous supporting tissue consists of collagen and elastin fibers

Alveolar Macrophage  Found within alveolar spaces and septa  Function in the phagocytosis and removal of unwanted material that gains access to the air spaces  After phagocytosing particles: o Most become trapped in mucus and coughed up as sputum o Others stay in septa o Others gain access to lymphatic system

Pulmonary Vasculature Large Elastic Pulmonary Artery  Pulmonary trunk, main right and left pulmonary arteries, major lobar branches  Similar to the aorta with prominent elastic lamellae as part of the tunica media  Layers are thinner and less substantial than the aortic counterpart since intravascular pressures are much lower Muscular Pulmonary Artery  Transition is at the point where bronchi lose cartilage plates and become bronchioles  Elastic fibers are disposed into internal and external elastic laminae  Tunica media is largely composed of smooth muscle and collagen Small Pulmonary Arterioles  Tunica media becomes thinner and eventually becomes discontinous

By: Sachi Estreller |Section B

3

UST FACULTY OF MEDICINE AND SURGERY Class of 2016 ORAL TISSUES 

Functions o Mastication  Ingestion, fragmentation, and moistening of food for swallowing o Speech and facial expression o Sensory reception o Breathing



Oral Mucosa   



Protective mucous membrane that contains many sensory receptors Lined by stratified squamous epithelium (keratinized in areas subject to considerable friction) Lamina Propria o In highly mobile areas: connected to underlying muscle by loose submucosal supporting tissue (eg. soft palate) o In fixed areas: connected to periosteum of bone by dense fibrous submucosa (eg. hard palate) Submucosa exhibit small salivary glands of both serous and mucous types



Lip  

 

External surface covered by hairy skin which passes through a transition zone to merge with the inner oral mucosa Vermillion Border o Transition zone which has a thin, lightly keratinized epidermis and richly vascularised dermis o Devoid of sweat and sebaceous glands Inner surface composed of thick stratified squamous epithelium with numerous accessory salivary glands in the submucosa Bundles of circumoral skeletal muscle is sandwiched between the internal and external surfaces

Palatal Mucosa  

Thick stratified squamous epithelium supported by tough, densely collagenous lamina propria Thrown into transverse folds called rugae to assist in mastication

Tooth Structure 

Crown o

Projects into oral cavity protected by enamel covering



o

Enamel  Hard, transluscent substance composed of parallel enamel rods of highly calcified material cemented together by interprismatic calcified material

o o o

Embedded in the bony alveolar ridge Invested by a thin layer of cementum Cementum  Amorphous calcified tissue connected to the bone of the alveolar socket by periodontal ligament  Generally acellular and becomes thicker at the root apex

Root

Dentine o Composed of calcified organic matrix similar to bone, but is more highly mineralized due to inorganic hydroxyapatite crystals o Dental Pulp  Contained in the central pulp cavity formed by dentine  Resembles primitive mesenchyme and contains stellate fibroblasts, reticulin fibers, fine collagen fibers, and ground substance  Richly vascularised and innervated o Dental Tubules  Radiate to periphery of dentine o Odontoblasts  Tall columnar cells on the surface of the dental papilla  Responsible for dentine formation  Initiate tooth formation by deposition of organic dentine between odontoblastic and ameloblastic layers  Dentine formed is pervaded by odontoblastic processes  dentine tubules o Ameloblasts  Induces enamel formation by calcification of dentine matrix Periodontal Membrane o Thin fibrous attachment between tooth root and alveolar bone that functions as the sling of the tooth within socket

By: Sachi Estreller |Section B

4

UST FACULTY OF MEDICINE AND SURGERY Class of 2016 o o

o

o

Permit slight movements of teeth and cushioning during chewing Sharpey’s Fibers  Run obliquely downwards from alveolar bone to cementum Epithelial Rests of Malassez  Small clumps of epithelial cells scattered throughout periodontal membrane

Gingiva 



  

Oral mucosa covering the upper part of the alveolar ridge that forms a tight protective cuff around the tooth Composed of thick stratified squamous epithelium that undergoes abrupt transition to a thin layer of epithelial cells at the tip of the free gingiva Attached Gingiva o Protective covering to upper alveolar bone Free Gingiva o Cuff around the enamel at the neck of the tooth Gingival Crevice o Potential space between the gingival cuff (free gingiva) and enamel of the crown of the tooth (cemento-enamel junction) o Crevicular epithelium easily breached by pathogenic organisms

Tongue 

 

Muscular organ covered by oral mucosa o Body of the tongue consists of interlacing bundles of skeletal muscle fibers o Mucous membrane bound to muscle layer by dense collagenous lamina propria o Small serous and mucous accessory salivary glands are scattered throughout the muscle and lamina propria Sulcus Terminalis o V-shaped groove that demarcated the anterior 2/3 from posterior 1/3 Anterior 2/3 o Filiform Papillae  Most numerous and appear as short bristles  Dense supporting tissue core with a heavily keratinized surface projection



Fungiform Papillae  Small red and globular  Thin, non-keratinized epithelium which is richly vascularized o Circumvallate Papillae  Largest and least common  Located immediately anterior to the sulcus terminalis  Contain most of the taste buds o Follicular Papillae  Rudimentary in humans o Von Ebner’s Glands  Aggregates of serous glands that open into the base of the circumvallate clefts  Secrete watery fluid that dissolves food and facilitates taste reception Posterior 1/3 o Smooth stratified squamous epithelium overlying lymphoid tissue termed as the lingual tonsils (part of Waldeyer’s Ring)

Salivary Glands 



Produce 600-1500 ml of saliva daily, which is a hypotonic watery secretion containing variable amounts of mucus, amylase and lysozyme, antibodies, and inorganic ions Salivary Secretory Unit o Consists of a terminal branched tubulo-acinar structure composed exclusively of either serous or mucous secretory cells o Terminal secretory units merge to form small intercalated ducts (cuboidal secretory cells) which drain into larger striated ducts (tall columnar cells) o Striated ducts  Function to reabsorb and secrete ions which produce hypotonic saliva with less Na and Cl and more K and HCO3 than plasma  Basal cytoplasm appears striated because of the presence of basal interdigitations of cytoplasmic processes of adjacent cells  Larger in serous glands than in mucous glands

By: Sachi Estreller |Section B

5

UST FACULTY OF MEDICINE AND SURGERY Class of 2016 o





Myoepithelial Cells  Force secretion from acinar lumen into duct system on contraction  Located between basal plasma membranes of secretory cells and basement membrane Minor Salivary Glands o Secrete continuously under local control o Scattered throughout oral mucosa Major Salivary Glands o Secrete in response to parasympathetic activity o Parotid Gland  Composed mainly of serous secretory units  Divided into numerous lobules with supporting tissue septa that convey blood vessels, nerves, and large excretory ducts  Main duct: Stensen’s o Sublingual Gland  Composed mainly of mucous secretory units  Large excretory duct lined by stratified cuboidal epithelium is present in tissue septum  As ducts merge to form major excretory duct, lining transforms into stratified squamous epithelium  Contains occasional adipocytes  Main ducts: Bartholin and Rivinus o Submandibular Gland  Composed of a mix of serous and mucous secretory units  Mixed secretory units are composed of mucous acini with serous demilunes  Mucous cell nuclei are condensed and flattened  Serous cell nuclei are rounded and centrallypositioned  Main duct: Wharton’s

By: Sachi Estreller |Section B

6

UST FACULTY OF MEDICINE AND SURGERY Class of 2016 GASTROINTESTINAL TRACT 

Functions to break down food for absorption into the body: o Ingestion o Fragmentation o Digestion o Absorption o Elimination

Structure of the GI Tract Functional Layers  Mucosa o Epithelium o Lamina Propria  Loose supporting tissue with diffuse lymphocytes and plasma cells (except for stomach) o Muscularis Mucosa  Keeps the mucosal surface and glands in constant gentle agitation which expels secretions from glandular crypts and enhances contact of epithelium and food for absorption  Submucosa o Loose collagenous and adipose supporting tissue o Contains the larger blood vessels, lymphatics, and nerves o No glands present except in esophagus and duodenum o Meissner’s Plexus  Supply mucosal glands and muscularis mucosae  Muscularis Propria o Smooth muscle usually arranged as ICOL. In the stomach, there is an inner oblique layer. o Auerbach’s Plexus  Between the two muscle layers  Supply surrounding smooth muscle  Adventitia o Outer layer of supporting tissue that conducts the major vessels, nerves, and variable adipose tissue Mucosal Forms in the GI Tract  Protective o Stratified squamous type o Found in oral cavity, esophagus, and anal canal







Secretory o Long, closely packed tubular glands that are simple or branched o Found only in the stomach Absorptive o Arranged into finger-like projections called cilli which increase the surface area with intervening short glands called crypts o Found in the small intestine Absorptive/ Protective o Arranged into closely packed, straight tubular glands and goblet cells specialized for water absorption and lubrication o Found in large intestine

Motility  Peristalsis initiated by Interstitial Cells of Cajal (pacemaker cells)  Modulated by ANS  Parasympathetic increases motility while sympathetic does the opposite

Esophagus     

Strong muscular tube that conveys food from the oropharynx to the stomach Thick stratified squamous epithelium Lamina propria is narrow and contains scattered lymphoid aggregates Submucosa is loose with many elastic fibers and small seromucous glands Muscularis propria is thick: ICOL o Bundles of skeletal muscle predominate in the upper 1/3 of esophagus o Smooth muscle predominate in lower 2/3

Gastro-esophageal sphincter  Physiologic sphincter  Factors: diaphragmatic contraction, greater intra-abdominal pressure, unidirectional peristalsis, maintenance of correct anatomical arrangements of the structures  Abrupt transition from stratified squamous epithelium to tightly packed glandular secretory mucosa  Muscularis mucosa, submucosa, and muscularis propria continue uninterrupted

By: Sachi Estreller |Section B

7

UST FACULTY OF MEDICINE AND SURGERY Class of 2016 o

Stomach   Rugae 

Cardia  

Distensible organ responsible for mechanical and chemical breakdown of food into chime Tall columnar epithelium

Longitudinal folds in the mucosa during nondistended state

Small area of mucus-secreting glands Cardiac glands are compound tubular in nature

Fundus and Body  Consist of glands that secrete acid-pepsin gastric juices; branched tubular in nature  Gastric glands o Simple tubular glands that extend from level of the muscularis mucosae to open into the stomach lumen via gastric pits of foveoli o 1-7 gastric glands may open into 1 gastric pit o Surface Mucous Cells  Short surface microvilli  Secrete bicarbonate o Neck Mucous Cells  At the neck and base of gastric glands  Have larger secretory granules and more polyribosomes than surface mucous cells o Parietal (Oxyntic) Cells  At isthmus of gastric glands  Secrete gastric acid and intrinsic factor  Eosinophilic cytoplasm with centrally-located nucleus; feature numerous mitochondria  Luminal plasma membrane form canaliculi with projecting short microvilli  Canaliculi are related to tubulovesicular system responsible for secretion of gastric acid o Chief Peptic (Zymogenic) Cells  Most common  At base of gastric glands  Secrete pepsin  Basophilic and granular cytomplasm with basallylocated nuclei; feature numerous RER

 

Pylorus  

Neuroendocrine Cells  At base of gastric glands  Secrete serotonin, etc. o Stem Cells  At neck of gastric glands  Replace all other cell types as needed Muscularis Propria o Inner oblique, middle circular, and outer longitudinal layers Mucosa o Devoid of lymphoid cells o With tall columnar mucus-secreting cells that protect epithelium from auto-digestion

Secrete two types of mucus and gastrin Gastric Glands o Coiled/ Convoluted branched tubular o Lined almost exclusively by mucussecreting cells o G cells that secrete gastrin are mainly found in the neck of the glands

Gastro-duodenal Junction  Anatomical sphincter  Sharp transition from glandular mucosa to villous mucosa  Pyloric sphincter is marked by a thickening of the circular layer of the muscularis  ICOL is continuous from pylorus to duodenum

Duodenum   



Main function is to neutralize gastric acid and pepsin Simple tall columnar epithelium with striated cuticular border and goblet cells Mucosa o Villi: longest and foliate o Characteristic villous form interspersed with short glands known as Crypts of Lieberkuhn that extend down to muscularis mucosae o Goblet cells least numerous among the three o Plicae circulares not prominent Brunner’s Glands o Unique feature of the duodenum o Extensive mass of coiled branched tubular glands in the submucosa o Tall columnar cells with mucigen-filled cytoplasm and basally located nuclei o Pass through the muscularis mucosae to open into the crypts between the villi

By: Sachi Estreller |Section B

8

UST FACULTY OF MEDICINE AND SURGERY Class of 2016 o



Secrete thin alkaline mucus, lysozyme, and epidermal growth factor Neuroendocrine Cells o Secrete secretin and cholecystokinin which promote pancreatic and bile secretion

 

Jejunum 

Mucosa o Villi: intermediate length, clevate/rounded o Goblet cells fairly present o Plicae Circulares most prominent here

Ileum 



Mucosa o Villi: shortest, conical o Peyer’s Patches predominate o Goblet cells most numerous among the three o Plicae Circulares fairly prominent in proximal ileum but absent in distal parts Ileocecal Junction o Abrupt transition from villiform lining to glandular lining o Ileocecal valve consists of a thickened extension of muscularis propria

Intestinal Villi and Crypts

  

Colon   





Simple columnar epithelium continuous with the crypts; Cores of villi are the extensions of lamina propria  Small lymphatic vessels drain into a single lacteal at the center of the villus. These lacteals transport absorbed lipid into the circulatory system via the thoracic duct Cell Types  Enterocytes o Most numerous and main absorptive cells; Tall columnar cells with surface microvilli o Main feature of cytoplasm is numerous free ribosomes, scattered mitochondria, and membranous vesicles containing lipoprotein droplets o Glycocalyx of microvilli prominent and acts as site for adsorption of pancreatic digestive enzymes o Transcytosis is an important mechanism for uptake of macromolecules from gut lumen into the blood  Involves endocytosis with transfer to the ECF at base of enterocyte

Goblet Cels o Produce mucin for lubrication and protection of epithelium Paneth Cells o At the base of crypts o Have prominent, eosinophilic apical granules o Defensive function: part of innate immune system; contain defensins, lysozyme, and phospholipase A Neuroendocrine Cell o Regulate GI motility and secretion Stem Cells o At the base of crypts; Replenish cell types Intraepithelial Lymphocytes o Mostly T cells for defense



Muscular layer still follows ICOL pattern but the longitudinal layer forms bands of teniae coli except in the rectum Indistinct cuticular border Glands o Consist of absorptive cells and mucussecreting goblet cells o Goblet cells predominate in the base while columnar absorptive cells predominate in the luminal surface Appendix o Presence of masses of lymphoid tissue in the mucosa and submucosa, especially present in the young o Mucosal glands less closely packed than in the large intestine Recto-anal Junction o Rectal mucosa is same as the rest of the large bowel except that it has even more numerous goblet cells o At the junction, abrupt transition to stratified squamous epithelium is observed o A transition from skin containing sebaceous glands to large apocrine sweat glands (peri-anal glands of Gay) is also seen. o Columns of Morgagni  Longitudinal folds found immediately above the anal valves o Circumanal Glands  Branched tubular glands that open at the recto-anal junction into small pits at the distal ends of the Columns of Morgagni

By: Sachi Estreller |Section B

9

UST FACULTY OF MEDICINE AND SURGERY Class of 2016 

ACCESSORY GLANDS OF THE GI SYSTEM Liver Functions  Fat metabolism: oxidation of TAGs, synthesis of plasma lipoproteins, cholesterol, and phospholipids  Carbohydrate metabolism: regulation of blood glucose concentrations  Protein metabolism: synthesis of plasma proteins, non-essential amino acids, detoxification of waste products  Storage: glycogen, vitamins, iron  Secretion: bile Structure  Structural integrity maintained by meshwork of extracellular matrix in the form of reticulin fibers (collagen type III), which becomes continuous with the liver capsule at the periphery  Glisson’s Capsule o Capsule composed of collagenous tissue o Portal Canal: thickened part of the Glisson’s capsule at the angles of the hepatic lobule that contains the portal triad  Hepatocytes o Main functional cell o Large polyhedral cells with round nuclei (peripherally dispersed chromatin and prominent nucleoli) o >50% of hepatocytes contain twice the normal complement of chromosomes within a single nucleus o Store significant amounts of glycogen and lipid o With numerous mitochondria and RER o Arranged as thin plates separated by fine vascular sinusoids  Hepatic Sinusoids o Low-resistance system of vascular channels that allows blood to come into contact with hepatocytes o Lined by flat endothelial lining cells with flattened nuclei o Endothelium is discontinuous and fenestrated, has no basement membrane, and is separated from the hepatocytes by the space of Disse o Cell Types:  Endothelial cells: flat nuclei and thin fenestrated cytoplasm  Kupffer cells: plump phagocytic cells with plump nuclei





Stellate cells of Ito: contains lipid droplets containing vitamin A; also produces ECM and collagen; causes fibrosis during cirrhosis

Hepatic Lobule o Anatomical unit of the liver o Hexagonal in shape and centered on a terminal cenrilobular venule o Portal tracts are positioned at the angles of the hexagon Hepatic Acinus o Structural unit of the liver o Berry-shaped and centered on the portal tract o Lies between two or more centrilobular venules o Divided into three zones:  Zone 1: highest perfusion, near the portal triad  Zone 2: intermediate  Zone 3: least perfusion, near the central vein; contain high levels of esterases and low levels of oxidative enzymes

Portal Tracts  Branched collagenous network through which the hepatic artery, portal vein, and bile ducts pass  Portal Vein o Largest of the three components of the portal tract o Lined by thin endothelial cells  Hepatic Artery o Thick-walled structures but smaller than portal vein  Bile Duct o Bile canaliculi contain ATPase and alkaline phosphatase; better demonstrated by silver impregnation o Bile canaliculi are located within each plate of hepatocytes drain into canals of Hering which is lined by simple cuboidal or columnar epithelium o Canals of Hering then drain to bile ductules which merge to form trabecular ducts  intrahepatic duct  right/left hepatic duct  common hepatic duct  common bile duct  Limiting Plate o Layer of hepatocytes immediately bordering the portal tract  Centrilobular Venules o Site where hepatic artery and portal vein drains

By: Sachi Estreller |Section B

10

UST FACULTY OF MEDICINE AND SURGERY Class of 2016 Gallbladder  

 

Muscular sac lined by simple columnar epithelium (basal nuclei) with microvilli Submucosa is loose and contains many elastin fibers, blood vessels, and lymphatics, which drain water reabsorbed from bile during the concentration process Muscular layer has oblique, longitudinal, and transverse orientations but no distinct layers Rokitansky-Aschoff Bodies o Normal feature that may be mistaken for malignant proliferating gland in the gallbladder

Pancreas 

Lobulated gland covered by a thin collagenous capsule which extends as delicate septa between the lobules

Exocrine pancreas  Consists of closely packed secretory acini  Acinar Cells o Each acinus is made up of an irregular cluster of pyramid-shaped secretory cells o Apices of the cells project towards the central lumen of a minute duct o With basal nuclei and basophilic cytoplasm  Centroacinar Cells o Terminal lining cells of intercalated ducts o Located at the centers of the acini  Intercalated Ducts o Simple low cuboidal epithelium o Smallest of the tributaries that drain into intralobular ducts  interlobular ducts Endocrine pancreas  Forms islets of langerhans most numerous in the tail of the pancreas  Main secretory products are insulin and glucagon  Islets of Langerhans o Composed of up to 3000 secretory cells supported by fine collagenous network with fenestrated capillaries each enclosed by a capsule o Each islet is supplied by three arterioles and drained by six venules o Secretory cells  Alpha cells (25%): glucagon  Beta cells (60%): insulin  Delta cells: somatostatin

By: Sachi Estreller |Section B

11

UST FACULTY OF MEDICINE AND SURGERY Class of 2016 ENDOCRINE SYSTEM 



Responsible for synthesis and secretion of hormones: o Protein and glycoprotein molecules o Small peptide molecules o Amino acid derivatives o Steroids General histological characteristics o Composed of islands of secretory cells of epithelial origin with intervening supporting tissue rich in vasculature o Cells have prominent nuclei and abundant mitochondria, ER, golgi bodies, and secretory vesicles

o

o

o

Pituitary Gland  

Bean-shaped gland at the base of the brain beneath the third ventricle, seated at the sella turcica Secretion of hormones under the influence of hypothalamus

Hormones Secreted  Hormones that act on non-endocrine tissue o Growth hormone o Prolactin o ADH o Oxytocin o Melanocyte-stimulating Hormone  Trophic Hormones (modulate other endocrine glands) o Thyroid Stimulating Hormone o Adenocorticotrophic Hormone o Gonadotrophic Hormone o Follicle Stimulating Hormone o Luteinising Hormone Anterior Pituitary  Also called adenohypophysis  Embryological origin: Rathke’s pouch  Pars tuberalis o Extension of the adenohypophysis that surrounds the neural stalk  Secretion of hormones controlled by hypothalamus by way of releasing hormones conducted from median hypothalamic eminence to the pituitary portal system (except prolactin secretion which is controlled by dopamine)  Cell Types o Somatotrophs  Most numerous  Secretes growth hormone  With secretory granules of moderate size

o

Mammotrophs  20% of cells; increase in number during pregnancy  Secretes prolactin Corticotrophs  20% of cells  Secretes ACTH split from a larger peptide known as proopiomelanocortin (also gives rise to lipotropins and endorphins)  Sparse secretory granules at the extreme periphery Thyrotrophs  5% of cells  Secretes TSH  Smaller and peripherallylocated granules Gonadotrophs  5% of cells  Secrete FSH and LH  Variably-sized granules

Pars Intermedia  Thin zone of tissue lying against posterior pituitary  Derived from Rathke’s Pouch  Composed of basophilic cells lying between the anterior and posterior hypothalamus  Contain secretory granules similar to corticotrophs, and produces proopiomelanocortin Posterior Pituitary  Also called neurophysis or pars nervosa  Composed of non-myelinated axons whose cell bodies are located in the hypothalamus o Axons are supported by glial cells called pituicytes  Secretes stored ADH (supraoptic nucleus) and oxytocin (paraventricular nucleus) from hypothalamus  Neurosecretion o Posterior pituitary secretes hormones in response to impulses from the hypothalamus o Neurosecretory granules are passed down from hypothalamus and accumulate in the Herring bodies, which are disended terminations of the axons

By: Sachi Estreller |Section B

12

UST FACULTY OF MEDICINE AND SURGERY Class of 2016 Thyroid Gland 

Butter-fly shaped gland that lies in the neck

Hormones Secreted  Tri-iodothyronine (T3) and Thyroxine (T4) o Iodine-containing hormones o T3 is the metabolically active form o Regulates the BMR and influence growth and maturation o Secretion dependent on TSH from anterior pituitary  Calcitonin o Regulates blood calcium levels in conjunction with PTH (lowers blood calcium levels) o Secretion dependent only on calcium levels Thyroid Follicle  Functional unit of the gland  Spheroidal structures composed of a single layer of cuboidal epithelial cells bounded by basement membrane  Store thyroglobulin, which is the storage form of T3 and T4  Lining epithelial cells o Synthesize glycoprotein component of thyroglobulin o Convert iodide to iodine o Inactive: simple flat or cuboidal o Active: tall and columnar Thyroid C Cell  Also called parafollicular cell  Found in thyroid as individual scattered cells in the follicle lining or as small clumps in the interstices between follicles  Secrete calcitonin

Parathyroid Gland 





Small oval endocrine glands closely associated with the thyroid gland; most important regulator of calcium Regulate serum calcium and phosphate levels by: o Increase osteoclastic resorption o Increase renal tubular reabsorption of calcium and inhibiting reabsorption of phosphate ions from filtrate o Promote absorption of calcium from the intestines Secretion is stimulated by decreased blood calcium levels

Structure  Thin fibrous capsule gives rise to septa that divide parenchyma into nodules and that carry vessels and nerves  Glandular Cells o Arranged as clusters, ribbons, or glands o Chief/ Principal Cells  Small with round central nuclei and eosinophilic cytoplasm  Synthesize and secrete PTH o Oxyphil Cells  Occur in nodules  With eosinophilic cytoplasm packed with mitochondria  Do not secrete PTH and increase in number with age

Adrenal Gland    

Small flattened endocrine glands closely applied to the upper pole of each kidney Has a dense fibrous capsule that provides support for the delicate collagenous framework supporting the secretory cells A prominent vein is characteristically at the center of the gland Supplied by the superior, middle, and inferior suprarenal arteries o Cortex is supplied by short cortical arteries o Medulla is supplied by long cortical arteries o All drain into the central vein

Adrenal Cortex  Secretes steroid hormones: mineralocorticoids, glucocorticoids, and sex hormones  Secretion controlled by ACTH (glucocorticoids) and the RAAS (mineralocorticoids)  Characteristics of Steroid Secreting Cells o Associated with fenestrated capillaries o Rounded cell nucleus with one or more nucleoli o Cytoplasm contains many large lipid droplets containing cholesterol esters o Numerous mitochondria and SER  Zona Glomerulosa o Outermost zone o Secretory cells arranged in irregular ovoid clusters separated by fibrous trabeculae o Cells have round nuclei and less cytoplasm (plenty SER and mitochondria, scanty lipid droplets) than cells in the next zone

By: Sachi Estreller |Section B

13

UST FACULTY OF MEDICINE AND SURGERY Class of 2016 o





Secretes mineralocorticoids (mainly aldosterone) Zona Fasciculata o Broadest of the three zones o Secretory cells arranged in parallel cords disposed at right angles separated by strands of collagen o Secretes glucocorticoids (mainly cortisol) and small amounts of androgens Zona Reticularis o Thin and innermost layer o Secretory cells are closely packed and irregularly arranged in cords separated by wide-diameter capillaries o Cells are smaller with less cytoplasm than cells in the previous zone o Secretes small amounts of androgens and glucocortocoids

Adrenal Medulla  Secretes catecholamines: adrenaline and noradrenaline  Secretion directly controlled by sympathetic NS  Chormaffin Cells o Secretory cells of the adrenal medulla o Composed of cells occurring in clusters with granular basophilic cytoplasm o Those secreting noradrenaline exhibit a more positive chromaffin reaction and a wider clear halo around the dense core granules in the cytoplasm than those secreting adrenaline

Diffuse Endocrine System 

Scattered system of neuroendocrine cells particularly important in the respiratory and GI tracts

Gastrointestinal Neuroendocrine Cells  Scattered in the mucosa of GI tract and in pancreatic and biliary ducts  Secrete hormones that regulate and coordinate GI activity in concert with the ANS (eg. CCK, VIP, NO)  May be endocrine, paracrine, or neurocrine Respiratory Neuroendocrine Cells  Involved in local and autonomically mediated regulation of respiratory function  Scattered individually in the epithelium or in clumps protruding into the airway  Secrete hormones such as serotonin, bombesin, and leu-enkephalin

Pineal Gland  





Small spherical gland that lies in the midline of the brain Synthesizes melatonin that induces rhythmical changes in the endocrine activity of the hypothalamus, pituitary, ovaries, and testes in response to light changes received by the retina Secretory Cells o Pinealocytes (Pineal Chief Cells)  Highly modified neurons  Round nuclei with granular cytoplasm  Granules contain melatonin and serotonin o Neuroglial Cells  Similar to astrocytes Pineal Sand o Basophilic extracellular bodies consisting of concentric layers of calcium and magnesium phosphate in an organic matrix o Characteristic of aging pineal gland

By: Sachi Estreller |Section B

14