2. DIGESTIVE SYSTEM part 1 Oral cavity, esophagus & stomach Department of histology, cytology and embryology KhNMU LECTURE

3. General description and significance The digestive tract is: The digestive tract is: a long tube extending from oral cavity to the anus and a long tube extending from oral cavity to the anus and associated glands. associated glands. Main functions are: ingestion, fragmentation, digestion, absorption of nutrients and elimination of waste products. Main functions are: ingestion, fragmentation, digestion, absorption of nutrients and elimination of waste products.

4. Classification and embryogenesis 3 compartments: 3 compartments: Anterior Oral cavity, pharynx, esophagus Anterior Oral cavity, pharynx, esophagus Middle Gastrointestinal tract Middle Gastrointestinal tract Posterior Last 1/3 rectum, anus Posterior Last 1/3 rectum, anus

5. Embryogenesis

6. Embryogenesis Gut – from endoderm, stomatodaeum, proctodaeum – from ectoderm Connective tissue, muscles are from mesoderm amnion yolk sac

7. Embryogenesis Yolk Sac Oral Plate Cloacal Plate foregut midgut hindgut Allantois Heart

8. General plan of structure FOUR principal membranes: FOUR principal membranes: Mucosa: Epithelium Mucosa: Epithelium Lamina propria Lamina propria Muscularis mucosae Muscularis mucosae Submucosa Submucosa Muscularis externa Muscularis externa Serosa or adventitia Serosa or adventitia

9. 1c 2 4 3a 2a 2b 3b 1a 1b

10. Mucosa: 1.epithelium (buccal)

11. Mucosa: 2. lamina propria – con.t. – nutrition, support, protection (GALT), absorption, secrition (glands), villi 3. muscularis mucosae Submucosa - Submucosa - con.t. - big bl.vessels, glands, nerve plexuses, lymphatic nodules, provides motility of mucosa Muscularis externa – circular, longitudinal layers Serosa or adventitia Serosa or adventitia

12. Oral Cavity consists of a number of suborgans Functions: Ingestion, STRUCTURE: Fragmentation 1. Mucosa Moistening 2. Submucosa Speech (not always present ! ) Facial expression 3. Muscularis ext. Sensory reception (facial muscles) Breathing 4. Adventitia (absent) (absent)

13. The outer surface (skin) of the lip is covered by thin skin (ts). The inner surface (oral) is lined by a mucosa The transitional zone oral side skin side low mag. oral skin sk ts ss bv sg lp Lip

14. Lip Lip Vermilion - “red” transitional zone In newborn there are small villi for sucking (Krok). The cheek is similar to the lip. red area ss p bv

15. Tongue Epithelium (E) & underlying ct. Skeletal muscle (SM) runs in 3 planes. Embedded in the skeletal muscle lie glands (G). Papillae. Most numerous are conical, keratinized filiform (f) papillae; function – general sensation fungiform and foliate papillae are scattered. fungiform and foliate papillae are scattered. At the sulcus terminalis, lie 8 -12 large circumvallate papillae (C). - Taste sensation E SM G C f

16. Tongue, filiform & fungiform papillae Tongue, filiform & fungiform papillae fili ct ss fungi nss Circumvallate papilla

17. Tongue papilla with taste buds papilla with taste buds high med fp tb

18. The mucosa (m) is tightly bound to the bone (b). The epithelium (ss) is disturbed in chewing and swallowing and so tends to be keratinized, and lamina propria forms deep papillae, protruding in the epithelium. The mucosa (m) is tightly bound to the bone (b). The epithelium (ss) is disturbed in chewing and swallowing and so tends to be keratinized, and lamina propria forms deep papillae, protruding in the epithelium. Hard Palate Maxilla unerupted tooth hard palate epithelium m b ss low med

19. Soft palate sm Epithelium sg oral cavity Its upper surface faces the respiratory passages - pseudostratified epithelium. Facing oral cavity epithelium is stratified squamous. Krok !

20. Lingual Tonsil Lingual Tonsil Lingual tonsil (T) locates on the dorsum of the tongue. Together with palatine, pharyngeal tonsils form "ring". At time of chronic inflammation may undergo tonsilectomy. ss c mg sk T

21. TOOTH

22. Tooth development Enamel organ (epith) Enamel organ (epith) Ameloblasts Ameloblasts Enamel Enamel Dental papilla Dental papilla Odontoblasts Odontoblasts Dentine Dentine Dental sac – cementum, Dental sac – cementum, pulp pulp

23. SALIVARY GLANDS Saliva : water, mucus, amylase, lysozyme, a/b, ions Saliva : water, mucus, amylase, lysozyme, a/b, ions I. Large salivary glands 3 pairs: parotid, submandibular, sublingual I. Large salivary glands 3 pairs: parotid, submandibular, sublingual function - IN RESPON ce TO PARASYMPATHETIC ACTIVITY II. Minor salivary glands f unction - CONTINUOUSLY II. Minor salivary glands f unction - CONTINUOUSLY

24. General structure Compound branched acinar or acino-tubular glands Compound branched acinar or acino-tubular glands Connective tissue capsule Connective tissue capsule Lobulated structure Lobulated structure Lobules contain secretory units and small ducts Lobules contain secretory units and small ducts Interlobular connective tissue with ducts and vessels Interlobular connective tissue with ducts and vessels

25. 5 Intercalated duct Striated duct, Next are interlobular and general Mucous acinus Serous acinus

26. Secretory unit Myoepithelial cells (contractile) surround secretory portions and small ducts – intercalated and striated Myoepithelial cells Nucleus

27. Parotid high low su n RER sd The parotid is a serous gland secreting amylase. Secretory unit (su) is acinar. Pyramidal acinar cells have round basally-placed nuclei (n) with abundant basal RER

28. low med Sublingual gland This gland has mucous & mixed secretory units but mostly mucous. high me d id itd n id sd Mixed acinus with a Mixed acinus with a Serous demilune Serous demilune msu

29. Submandibular gland It is predominantly serous gland shows blue, pure serous acini (sa) & pale, mucous and mixed with serous demilunes (m/s). low high med lobule id ed sa m/s

30. sublingual gland Submandibular gland Striated duct demilune Demilune Intercalated duct Parotid gland Sublingual gland Compare! Demilune Striated duct

31. Esophagus (= Pharynx) 6-7 longitudinal folds. The muscularis externa. The upper 1/3rd is composed of skeletal muscle; the lower 1/3rd - smooth muscle; the middle 1/3rd shows a blending of the two varieties of muscle. Epithelium is stratified squamous nonkeratinized

32. HEsophagus 1) Mucosa- epithelium, lamina propria & muscularis mucosae, 2) Submucosa, 3) Muscularis externa 4) Adventitia

33. Esophagus Mucosal cardiac glands (mg) are in the lamina propria (lp) (mm) in the upper and lower thirds of the esophagus. Mucosal cardiac glands (mg) are in the lamina propria (lp) (mm) in the upper and lower thirds of the esophagus. If they are not fully effective, the excessive reflux results in pyrosis (heartburn) – the rise of the gastric contents upward toward the neck. If they are not fully effective, the excessive reflux results in pyrosis (heartburn) – the rise of the gastric contents upward toward the neck. mg lp ss mm sm me

34. Esophagus A mucous esophageal glands proper (mg) lie in the submucosa (s). lie in the submucosa (s). mg s mm me

35. muscularis externa (me). = smooth (sm) & skeletal muscle (sk). lymphatic nodules (L) are in the mucosa (m). L sub me sm sk m HEsophagus, H middle 1/3rd - med. mag..

36. Esophagus The enteric nervous system is extensive and its neurons and fibers form in the submucosa (Meissner’s plexus) (M') and in the muscularis externa (Auerbach’s plexus) (A'). M' A' str.sq.epi musc. muc. submuc.muscul. externa. submucosal gl. lymphatic nodule lumen med high

37. H Esophagus/Stomach junction. - Epithelium is changed from stratified squamous to simple columnar (sc). 1 2 3 E E S S sc gp low medhigh

38. Stomach - general The process of digestion essentially begins in the stomach; little absorption and excretion also occur here. The process of digestion essentially begins in the stomach; little absorption and excretion also occur here. The stomach is composed of a mucosa, submucosa, muscularis externa & serosa. The stomach is composed of a mucosa, submucosa, muscularis externa & serosa. The mucosal lining is a simple columnar secretory epithelium (mucous). The mucosal lining is a simple columnar secretory epithelium (mucous). Folds (rugae), gastric pits, mammilated areas. Folds (rugae), gastric pits, mammilated areas. Glands vary in different regions of the stomach. Glands vary in different regions of the stomach.

39. Stomach Stomach mucosa: mucosa: ``` epithelium ``` epithelium lamina propria: gastric glands ; lamina propria: gastric glands ; glands glands muscularis mucosae: both circular and longitudinal layers of SM. muscularis mucosae: both circular and longitudinal layers of SM. submucosa: submucosa: muscularis: the inner oblique layer, circular layer and longitudinal layer of SM. muscularis: the inner oblique layer, circular layer and longitudinal layer of SM. serosa serosa

40. Stomach, mucosal lining & gastric pits Stomach, mucosal lining & gastric pits Gastric pits (gp) are invaginations of a simple columnar epithelium The mucus blanket which protects the lining from stomach acids is present here. gp sc

41. Lamina propria contains glands Lamina propria contains glands fundic glands (in the body, fundus) secrete the enzymes and acid of the stomach. While cardiac and pyloric glands predominantly secrete mucus. fundic glands (in the body, fundus) secrete the enzymes and acid of the stomach. While cardiac and pyloric glands predominantly secrete mucus. The fundic glands are simple tubular. The fundic glands are simple tubular. They contain 4 cell types: They contain 4 cell types:

42. 1. Mucous neck cells 2. Chief cells, or zymogenic cells columnar and basophilic cells - in the body of the glands. columnar and basophilic cells - in the body of the glands. produce pepsinogen and lipase. produce pepsinogen and lipase. 3. 3. Parietal cells secrete hydrochloric acid ( HCL ) and intrinsic factor. The latter is necessary for absorption of vitamin B 12 in the ileum

44. 4. Enteroendocrine cells (APUD) 20 different types 20 different types 4 principal hormones: 4 principal hormones: Gastrin Hcl secretion Gastrin Hcl secretion Secretin, cholecystokinin (CCK), gastric inhibitory peptide (GIP) pancreatic and gallblader activity and gastric secretion Secretin, cholecystokinin (CCK), gastric inhibitory peptide (GIP) pancreatic and gallblader activity and gastric secretion

45. Pernicious anemia follows the absence of parietal cells (i.e. loss of epithelium due to gastric ulcer) Disturbance of different cells may call the different pathology. Disturbance of different cells may call the different pathology. Digestion of different substances begins in different regions. Digestion of different substances begins in different regions.

46. Fundic stomach The lowest mag. shows the mucosa (m), submucosa (sm) with folds called rugae (r) & the muscularis externa (me). At higher mag. gastric pits (gp), fundic glands (fg), & muscularis mucosa (mm) comprises the mucosa. Outside is the submucosa (sm) and muscularis externa (me). 2 m sm r me gp fg mm sm me low med

47. Fundic stomach mucosa In fundic stomach, gastric pits occupy about 1/5 the mucosa; fundic glands comprise the remaining 3/4ths. gastric pit fundic gland Isthmus Neck Base

49. Cardiac Stomach, Cardiac Stomach, Gastric pits occupy ½ of mucosa. Gastric glands are simple tubular and slightly branched Cells are mucus-secreting and occational endocrine gastric pit cardiac glands sc mm

50. Stomach, pyloric Gastric pits occupy 3/4ths the depth of the mucosa; the remaining 1/4th are pyloric glands – short and branched. The major cell of the gland is the pale mucous (mn); parietal cells are absent as the pyloric stomach nears the intestine. gastric pit gastric gland mn low

51. Fundic Stomach, nerve supply, - med & high mag Fundic Stomach, nerve supply, - med & high mag Elements of the submucosal (s) and myenteric (m) nerve plexuses are present. fundic glands musc. mucosa submucosamuscularis externa inner middle outer s m smooth muscle artery vein