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Digestive System
1. General organization of the internal organs
2. Digestive system – overview
3. Anterior digestive tract
4. Gastrointestinal tract
5. Rectoanal region
6. Hepatobiliary system
7. Peritoneum
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov
Internal organs of human body
2
� Internal organs – viscera (splanchna):
� organs of the digestive, respiratory
and urogenital systems
� located primarily in the thoracic and
abdominal cavities
� functions – organs of vegetative state
(vegetative organs)
� metabolism
� reproduction
� structural and functional differentiation
� hollow organs (tube or pouch) or
parenchymal organs
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov
Internal organs
3
� Digestive system:
� from cranial to caudal end of the body,
mostly in the abdominal cavity
� Respiratory system:
� mainly in the thoracic cavity
� Urogenital system:
� lower part of the
abdominal cavity
and in the pelvis
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov 4
General structure of hollow organs
� mucosa, tunica mucosa:� lamina epithelialis – covering epithelium
� lamina propria – loose connective tissue� blood and lymph vessels
� lymph follicles (MALT, GALT, BALT)
� elastic fibers, nerves and nerve structures
� mucosal glands – in stomach and gut
� lamina muscularis mucosae – smooth muscle (membrana elastica)
� tela submucosa� blood vessels
� submucosal plexus (plexus of Meissner)
� glands – in esophagus and duodenum
� tunica muscularis� inner circular layer
� myenteric plexus (plexus of Auerbach)
� outer longitudinal layer� tunica serosa (adventitia)
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov
General structure of parenchymal organs
� Solid organs, organa solida:� epithelial tissue – parenchyma� connective tissue – stroma� blood and lymph vessels� nerve structures
� Structure principle:� structural units
� lobules, segments, lobes� fibrous capsule
� adventitia or serosa� Main functions:
� secretion and excretion� gas exchange� formation of sex cells
� Representatives:� liver, pancreas� kidney, spleen� ovary, glands
5
Parenchyma vs. Stroma
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov
Digestive system
6
� Digestion:
� mechanical breakdown of food
� chemical breakdown – enzymes
� traveling down of the bolus (peristalsis)
� absorption of the chyme
� elimination of waste material (defecation)
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov
Digestive system
7
� Digestive system, systema digestorium, apparatus digestorius:
� alimentary canal – length 9 m
�mouth
� anus
� accessory digestive glands:
� salivary glands
� liver
� pancreas
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov 8
Alimentary canal
� Anterior part:
� mouth and oral cavity
� throat, pharynx
� gullet (esophagus)
� Middle part – GI tract:
� stomach
� small intestine
� Posterior (terminal) part:
� large intestine,
incl. rectum and anus
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov
Oral cavity, cavitas oris
9
� Cavitas (cavum) orisGr. stoma, stomatos:� in the facial region of the head
� rima oris
� isthmus faucium
� Parts of the oral cavity:� oral vestibule, vestibulum oris
� oral cavity proper, cavitas oris propria
� boundarieso gums and teeth
o hard palate
o part of the soft palate
o diaphragma oris
� contento tongue
o teeth
� fauces – the troat
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov
Lips, labia oris
10
� Macroscopic anatomy:� oral fissure
� angle of mouth
� labial frenulum
� Upper lip, labium superius
� Lower lip, labium inferius
� Structure – orbicularis oris muscle:
� cutaneous portion – hairy skin
� marginal (red) portion
� mucosa– stratified squamous epithelium
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov
Cheeks, buccae
11
� Structure – two membranous walls:
� enclose the mouth laterally
� similar to lips structure
� skin
� muscle layer – buccinator muscle
� subcutaneous fat tissue, –
buccal fat pad (Bichat)
� buccal mucosa
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov 12
Palate� Palate, palatum:
� separates the oral cavity from the nasal cavity
� palatum durum
� palatum molle
� Hard (bone) palate, palatum durum (osseum)– anterior ⅔:
� processus palatinus maxillae
� lamina horizontalis ossis palatini
� transverse palatal ridges
� Soft palate, palatum molle– posterior ⅓
� velum palatini with uvula
� pharyngopalatine arch
� skeletal muscle
� glandular tissue, no bone
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov 13
Gums, gingivae
� Gums, gingivae:
� pars fixa
� pars libera s. marginalis
� Macroscopic anatomy:
� gingival margin
� gingival sulcus
� papilla gingivalis (interdentalis)
� vestibular
� oral
� Microscopic anatomy:
� lamina epithelialis
� stratified squamous nonkeratinized
epithelium
� lamina propria – papillae
� abundant blood supply
� rich innervation
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov
Teeth, dentes
14
� Teeth, dentes (Gr. odus, odontos):� mechanical breakdown (chew) of food
� help in phonation
� derivatives of oral mucosa
� Characteristics of human dentition:
� close contact between teeth
� heterodont – teeth differ morphologically
� diphyodont – two successions of teeth
� in a process of evolution – reduction in number
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov
Human dentition
15
� Permanent teeth, dentes permanentes:
� 32 teeth into two symmetrical halves
� upper dental arch, arcus dentalis superior
� lower dental arch, arcus dentalis inferior
� anatomical and functional groups:
� incisors, dentes incisivi
� canine (dogteeth), dentes canini
� premolars, dentes premolares
�molars, dentes molares
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov
Human dentition
16
� Deciduous (milk) teeth, dentes decidui:
� the first set of teeth in the growth
development of humans
� 20 teeth into two symmetrical halves
� distinguishing features (traits):
� similar morphology but smaller in size
� slightly blue tone of enamel
� shorter roots
� wider root canals and cavity
� anatomical and functional groups:
� incisors, dentes incisivi - 2
� canine teeth, dentes canini – 1
�molars, dentes molares – 2
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov
Basic tooth structure
17
� Principal parts of a tooth:� tooth crown, corona dentis – surfaces
� margo incisialis (incisivus) – incisors
� facies occlusalis (masticatoria) –premolars and molars
o tuberculum dentale (cuspis dentalis)
� facies vestibularis (labialis, buccalis)
� facies lingualis
� facies contactus (mesialis et distalis)
� anatomical vs. clinical crown
� tooth neck, cervix dentis� root, radix dentis – in dental alveolus
� apex radicis dentis
� cavity – cavitas dentis(pulparis)� cavitas coronae
� canalis radicis dentis
� tooth pulp, pulpa dentis� pulpa coronalis
� pulpa radicularis
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov 18
Tongue, lingua (Gr. glossa)
� Parts of the tongue:� body, corpus linguae � apex linguae
� root of tongue, radix linguae
� divided by the sulcus terminalis
� Surface anatomy of the tongue:� upper surface, dorsum linguae
� pars presulcalis (anterior, oralis)
� pars postsulcalis (posterior, pharyngealis)
� sulcus terminalis � foramen cecum
� sulcus medianus linguae
� lower, facies inferior linguae
� plica fimbriata
� frenulum linguae
� caruncula sublingualis � plica sublingualis
� margin of the tongue, margo linguae
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov 19
Papillae of the tongue
� Papillae linguales – 4 distinct types:
� papillae filiformes (conicae)
� papillae fungiformes
� papillae vallatae
� papillae foliatae
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov 20
Taste perception� taste buds, caliculi (gemmae)
gustatorii – 2000-9000:
� vallate papillae – most numerous,
plentiful in the posterior ⅓ of tongue
� fungiform and foliate papillae
� soft palate, epiglottis and pharynx
� reduction in number (up to ⅓) with age � our sense of taste
can and do change over time!
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov 21
Glands of the tongue� Glandulae linguales – minor salivary glands:
� mixed (seromucous) glands – near the tip anterior lingual (Nuhn’s) glands
� serous glands – in the vallate papillaegustatory (von Ebner’s) glands
� mucous glands – in the tongue root posterior lingual (Weber) glands
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov 22
Lingual tonsil
� Tonsilla lingualis:
� small, rounded mass
of lymphoid tissue in the
posterior ⅓ of the tongue
� tonsillar papillae, tonsillar
crypts � Weber’s salivary glands
� covered with stratified squamous epithelium
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov 23
Muscles of the tongue� Skeletal (extrinsic) lingual muscles – move the tongue:
� m. genioglossus – most well developed
� m. hyoglossus
� m. styloglossus
� m. palatoglossus
� m. chondroglossus – inconstant
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov 24
Muscles of the tongue� Proper (instrinsic) lingual muscles – alter its shape:
� m. longitudinalis superior
� m. longitudinalis inferior
� m. transversus linguae
� m. verticalis linguae
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov 25
Salivary glands
� Small salivary glands, glandulae salivariae minores:
� mixed glands:
� labial
� buccal
�molar
� anterior lingual glands (Nuhn)
� serous glands:
� von Ebner’s glands in the tongue
� mucous glands:
� palatine glands
� posterior lingual glands (Weber)
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov 26
Salivary glands� Large salivary glands, glandulae salivariae majores:
� Parotid gland,
glandula parotidea (parotis)
� Submandibular gland,
glandula submandibularis
� Sublingual gland,
glandula submandibularis
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov
Fauces, fauces
27
� Isthmus faucium
� Fauces:
� velum palatinum – superiorly
� uvula palatina
� palatoglossal arch
� palatopharyngeal arch
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov
Waldeyer’s tonsillar ring
28
� Anulus lymphoides Waldeyeri:
� lingual tonsil
� pharyngeal (adenoid) tonsil
� tubal tonsil
� palatine tonsil
� NALT – Nasal-Associated Lymphoid Tissue
von Waldeyer(1836-1921)
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov
Throat, pharynx
� food and air-conduction crossroad
� part of the digestive and respiratory systems
� important in vocalization
� cone-shaped muscular membranous sac:
� length– 12-15 cm
�diameter –
�upper portion: 3.5 cm
�lower portion: 1.5 cm
29
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov
Macroscopic anatomy
� Three general areas:� epipharynx (nasopharynx) � mesopharynx (oropharynx)� hypopharynx (laryngopharynx)
30
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov
Pars nasalis pharyngissynonyms: nasopharynx, epipharynx
� Part of the respiratory system:
� fornix pharyngis –
tonsilla pharyngealis (adenoidea)
� tonsilla tubaria
31
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov
synonyms: oropharynx, mesopharynx
Pars oralis pharyngis
32
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov
Pars laryngea pharyngissynonyms: laryngopharynx,
hypopharynx
33
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov
Muscles of the pharynx� Skeletal muscles� tunica muscularis pharyngis:
�deep layer of longitudinally oriented muscles� superficial layer of
circular skeletal muscle
� Two functional groups:� mm. levatores pharyngis� mm. constrictores pharyngis
34
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov
� Straight muscular tube 25-30 cm long:�begins at the level of
cricoid cartilage – C6
�pass through the mediastinum and penetrates the diaphragm– Th10
�meets the stomach – Th11
Gullet, esophagus
35
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov
Macroscopic anatomy
36
� Anatomical parts:� cervical part – 5-6 cm� thoracic part – 16-19 cm� abdominal part – 1-4 cm
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov
Anatomical constrictions
37
� Three anatomical constrictions:� pharyngoesophageal – 15 cm from the incisors
� broncho-aortic– 24 cm from the incisor teeth
� phrenic – 40 cm from the incisor teeth
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov
1. Aortic – at the site of bifurcation with the aortic arch
2. Cardiac – the lower entrance to the stomach
Physiological constrictions� Two physiological constrictions –
due to the muscle contractions of the esophagus
38
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov
Microscopic structure
� Lamina epithelialis mucosae:
stratified squamous nonkeratinizingepithelium – 20-24 layers
� Lamina propria mucosae:
� cardiac glands
� Lamina muscularis mucosae:� longitudinal smooth muscles
� Tela submucosa:� esophageal glands
� plexus submucosus (Meissneri)
� Tunica muscularis – transition
� internal circular layer
� external longitudinal layer
� plexus myentericus (Auerbachi)
� Tunica adventitia:� loose connective tissue
� serosa below the diaphragm
39
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov
Stomach, gaster (ventriculus)
40
� the dilated portion of the alimentary canal, pouch-like, J-shaped organ:� stores food – 1-1.7 l
� in the upper left part of the abdomen, below the diaphragm
� 4 anatomical regions:� cardiac region, cardia
� fundic region, fundus
� body, corpus
� pyloric region, pylorus
� Two walls:� anterior
� posterior
� lesser and greater curvature
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov 41
Microscopic structure� 3 histological regions:
� cardiac�pars cardiaca
� fundic� fundus et
� corpus gastricum
�pyloric�pars pylorica
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov
� gastric mucosa, tunica mucosa� tela submucosa
� muscle layer, tunica muscularis� serosa, tunica serosa
42
Gastric wall
� Three tissue layers:
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov
� lamina epithelialis – simple columnar glandular epithelium:
surface mucous cells (4-7 days) и pit cells
� lamina propria mucosae – gastric glands
� lamina muscularis mucosae – gastric rugae
43
Gastric mucosa
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov 44
Gastric glands� gastric glands proper – 35 million
glandulae gastricae propriae� pepsinogen and hydrochloric acid� gastric intrinsic factor
� cardiac – glandulae cardiacae
� pyloric – glandulae pyloricae, 3.5 million
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov
� Tunica serosa:� part of peritoneum
Histological structure� Tela submucosa:
� connective tissue withblood and lymph vessels
45
� Tunica muscularis:� inner oblique layer, fibrae obliquae
� middle circular layer (m. sphincter pyloricus)
� outer longitudinal layer (stratum longitudinale)
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov
Small intestine, intestinum tenue
46
� Small intestine – convoluted tube:
� longest part of the digestive tract
� from pylorus to the
ileocecal valve
� length – 6-8 m
� diameter – 4-3 cm
� capacity – 4 l
� functional peculiarities
� Three portions:
� the duodenum,
duodenum – first 25-30 cm
� the jejunum, jejunum – 2/5
� the ileum, ileum – 3/5
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov 47
� Location and anatomical parts:
� shortest, widest and most fixed intestinal part
� C-shaped curve around pancreatic head
� superior part – 5 cm
� descending – 7.5 cm
� horizontal – 10 cm
� ascending – 2.5 cm
Duodenum in situ
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov 48
Mesenteric small intestine
� Mesenteric small intestine:
� intraperitoneal position
� projected in:
� regio mesogastrica
� regio hypogastrica
� The jejunum, jejunum:
� horizontal arrangement of its loops
� located largely toward the upper left
of the intestinal coils
� begin from duodendojejunal flexure (L2)
� The ileum, ileum:
� vertical arrangement of its loops
� located largely toward the lower right
of the intestinal coils
� ends at the ileocecal junction (L4)
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov 49
Intestinal wall
� tunica mucosa – spiral ridges� circular folds, plicae circulares
� tela submucosa� tunica muscularis� tunica serosa
� Three major layers:
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov 50
Intestinal mucosa� Mucosa, tunica mucosa:
� intestinal villi – cells
� intestinal glands
� duodenal glands
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov
Large intestine, intestinum crassum
51
� Large intestine:
� end part of the digestive tract
� length 1.5-2 m, diameter 6.5 cm
� capacity 2-3 l
� functions:
� formation and evacuation of bolus
� water absorption
� degradation of food matter –
cellulose, waste material, mucus
� Parts:
� cecum (caecum)
� colon
� rectum
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov 52
Cecum and appendix
� Cecum:� blind pouch in lower
right abdominal quadrant
� inferior to ileocecal valve
� intraperitoneal position
� Appendix vermiformis:
� blind tube 7-8 cm long
� intraperitoneal � mesoappendix
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov 53
Colon
� Four sections:� ascending, colon ascendens
� transverse, colon transversum
� descending, colon descendens
� sigmoid, colon sigmoideum
� Anatomy:� longitudinal ribbon-like muscular strips,
taeniae coli
� taenia libera
� taenia omentalis
� taenia mesocolica
� pouches, haustrae coli
� club-like fatty pouches of peritoneum, epiploic appendages
� semilunar folds, plicae semilunares coli
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov 54
Colon wall
� mucosa, tunica mucosa� intestinal glands, no intestinal villi
� tela submucosa� submucosal plexus (Meissner)
� muscle layer, tunica muscularis� internal circular layer� external longitudinal layer –
in teniae� myenteric plexus (Auerbach)
� serosa, tunica serosa (adventitia)
� Three major layers:
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov 55
Rectum, Gr. proctos� Anatomy of recto-anal region:
� 3 transverse folds, rectal valves� length 12-15 cm, S-shaped� rectal ampulla� anal canal – final 3 cm
� longitudinal ridges, anal columns
� anal sinuses
� anal verge, anus
� internal and external anal sphincter
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov 56
Microscopic anatomy
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov
Liver, hepar
57
� Largest internal organ and largest gland in the human body:� volume – ~1500 cm3
� weight – 1.5-2.4 kg� unequal size and shape� soft, reddish-brown, triangular organ
� Location:� beneath the diaphragm� right hypochondriac and epigastric regions
� Dual blood supply:� 70-80% – hepatic portal vein:
venous blood from the spleen, entire gastrointestinal tractand its associated organs
� 20-30% – hepatic arteries: arterial blood
� > 500 vital functions – production of bile, major role in metabolism
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov
Gross anatomy
58
� Two surfaces:� superior diaphragmatic
� inferior visceral – porta hepatis
� posterior – bare area
� Hepatic lobes:� right lobe
� left lobe
� quadratus and caudatus lobes
� Hepatic segments
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov
Microscopic anatomy
� serosa, tunica serosa
� fibrous capsule of Glisson,tunica fibrosa
� hepatic lobules, lobuli hepatis:
� total number – ~1 000 000
� shape – hexagonal
� size – 0.7 x 2 mm
� content:
• parenchyma, hepatocytes
• central vein
• sinusoids
59
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov
Functional units of liver
60
� “classical” lobule –anatomical model
� portal lobule –
bile secretion
� liver acinus –
blood flow and metabolic
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov
Gallbladder, vesica biliaris (fellea)
61
� hollow pear-shaped organ:� concentrates bile
� aids in fat digestion
� volume: 40-60 cm3
� three sections:� fundus� body, corpus� neck, collum
� cysticduct,ductus cysticus
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov
Biliary tree� bile canaliculi� bile ducts
(canals of Hering)� interlobular bile ducts� left and right hepatic ducts� common hepatic duct� cystic duct� common bile duct
62
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov
Pancreas � Gr. πάγκρεαςpan “all”, kreas, “flesh”
63
� A large glandular organ:� weight – 80 g (30-180 g)
� size – 15 cm long, 2.5 thick
� exocrine and endocrine gland
� location – retroperitoneal:
� hidden behind the stomach
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov
Macroscopic anatomy
64
� 5 anatomical parts:� head, caput pancreatis� uncinate process� neck, collum pancreatis� body, corpus pancreatis� tail, cauda pancreatis
� Pancreatic structure:� exocrine part – pancreatic acini� endocrine part – pancreatic islets
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov
Exocrine pancreas, pars exocrina pancreatis
65
� Exocrine tissue – pancreatic juice:
� secretory acini – serous acinar cells
� duct system:� intercalated ducts
� intralobular ducts
� interlobular ducts
� main pancreatic duct (of Wirsung)
� accessory pancreatic duct (of Santorini)
� pancreatic lobules, connective tissue septa
� thin pancreatic capsule, capsula pancreatis
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov
Endocrine pancreas, pars endocrina pancreatis
66
� Islets of Langerhans, insulae pancreaticae:� > 1 million (1-2% of the volume)� weight ~ 1 g� diameter 100-300 µm � most numerous in the tail
� Cell types:� A cells – 15-20%, glucagon� B cells – 60-80%, insulin� D cells – 5-10%, somatostatin� PP cells – 2-5%, pancreatic polypeptide� D1 cells – 0.5-1%, VIP� EC cells� G cells – gastrin, Y cells – ghrelin
SPLANCHNOLOGY
Prof. Dr. Nikolai Lazarov
Peritoneum� Serous membrane:
� visceral peritoneum� parietal peritoneum� meso- and ligaments
� Peritoneal cavity � peritoneal fluid� Microscopic anatomy:
� mesothelium� subserous connective tissue
� Peritoneal positions of organs:� intraperitoneal� mesoperitoneal� retroperitoneal, extraperitoneal
67
Voltaire
(1694-1778) 68
“The fate of a nation has often depended on food or bad digestion of a prime minister”
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