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1

What are the functions of salivary glands
where are they found and what do they secrete

- moisten food (assists mastication)
- lubricate bolus (mass of food before swallowing) during deglutition (swallowing)
• scattered salivary glands in lips, cheeks, soft palate and tongue
- secretions mostly mucous (carbohydrate-rich)
• majority of saliva from distinct large salivary glands:
- secretions mostly serous (watery and protein-rich)

2

List the 4 main salivary glands

1) parotid gland
2) mandibular gland
3) sublingual gland
4) zygomatic gland

3

parotid gland where located, what species larger in, how does primary duct travel to oral cavity in different animals - what type of secretions

located superficially, ventral to ear
• larger in herbivores than in carnivores relative to body size
• primary duct travels to oral cavity:
- Carnivore - across lateral surface of masseter muscle in dog ⇒ opening in vestibule adjacent to upper fourth premolar tooth (pink in image number 1) - same opening in all species
- Herbivore - medial to ventral border of mandible in horse and ox ⇒ crosses ventral border of mandible laterally then goes through buccanator muscle ⇒ enters oral vestibule as for dog, horses only 3 upper premolars however many have a wolf tooth so still upper 4th premolar
purely serous except dog

4

mandibular gland where located, larger in what animals, where does duct open - what type of secretions

Medial to parotid gland and much more superfical in the dog so more obvious to see, in horse underneath the parotid gland
• located at angle of jaw
• deeper and larger in herbivores
• duct opens at sublingual caruncle
- mixed serous and mucous

5

Sublingual gland - what parts where found and where does duct open - what type of secretion

2 parts - monostomatic (single primary duct) and polystomatic (multiple ducts) parts in most species right underneath the oral mucosa in oral cavity
• ducts run along floor of oral cavity and open adjacent to frenulum monostomatic in dog
- mixed serous and mucous

6

Zygomatic gland where found, where does duct open, what type of duct system does it have

present in dog and cat lateral to the ear
• medial to zygomatic arch (in orbit)
• duct opens opposite last upper molar
• branching duct system:

7

how does a duct system work what cells are involved

acinus ⇒ intercalated duct ⇒ striated duct (larger) ⇒ interlobular duct (in connective tissues between lobules)⇒ primary duct
• secretory cells arranged in acini (clusters of cells arranged around a lumen) surrounded by basement membrane
• contain serous or mucous acini (secreting cells), or both

8

What are the types of acini and describe their structure and histology

Serous
• cells pyramidal - 2D triangles
• round basal nuclei
• basophilic perinuclear cytoplasm - protein rich
• secretory granules in apical cytoplasm
Mucous
• cells swollen with mucous secretions (carbohydrate - don't take up H&E stain so clear) at apical part of cell which pushes nuclei basally
• flattened basal nucleus
Mixed glands
• individual acini composed entirely of serous or mucous cells, or both:
• serous demilunes (half-moon shape) in mixed acini

9

the histology of intercalated ducts, striated ducts and interlobular ducts

Intercalated duct: low cuboidal epithelium, thin wall, variable cytoplasm - much less
Striated duct: columnar epithelium with basal striations due to alignment of mitochondria in cytoplasm, more cytoplasm than intercalated ducts
Interlobular duct: first simple columnar and as they merge towards primary duct becomes stratified columnar

10

what innervation is involved with salivary gland secretion

• secretion under autonomic (parasympathetic) control:
o cranial nerve VII (facial) ⇒ mandibular, sublingual, buccal and zygomatic glands
o cranial nerve IX (glossopharyngeal) ⇒ parotid gland

11

pharynx what group of muscles form the wall and innervation

constrictors, dilator, shortener
Motor and sensory: - contributions from cranial nerves IX and X (vagus).

12

steps in deglutition

1) Bolus of food prepared by mastication and insalivation
2) apex of tongue pressed against palate
3) rapid contraction of mylohyoideus and extrinsic muscles of tongue (in brown) to propel food into pharynx
4) contact of bolus with pharyngeal mucosa sets off reflexes
5) soft palate raised, glottis (narrowest part of larynx) closed, hyoid apparatus drawn rostrally, pharynx shortened (by pharyngeal shorteners) - bolus doesn't move but pharynx comes forward to engulf food
6) bolus moved into oesophagus by pharyngeal constrictors - rostral to caudal
7) wave of peristalsis within oesophagus conveys bolus to stomach

13

oesophagus other name, function and structure

• also known as gullet
Function - to conduct food from the mouth to the stomach
Structure- simple muscular tube that runs from the pharynx to the stomach in 3 segments:
o cervical, thoracic and abdominal

14

cervical segment of the oesophagus where is it located and what line does it follow

from pharynx to thoracic inlet (surrounded by 1st ribs, 1st sternebra and 1st thoracic vertebra)
o begins dorsal to cricoid cartilage of larynx (immediately rostral to beginning of trachea)
o follows trachea down neck, initially inclining to left
o medial to left jugular groove (over the surface of the jugular vein)
o returns to median position above trachea at about level of 1st rib

15

thoracic segment of the oesophagus where is it located and what does it follow

o runs within mediastinum in thorax (mediastinum formed from membranes that separate thorax into two pleural cavities and surround unpaired structures such as heart, aorta and oesophagus)
o passes over base of heart (dorsal)
o crosses right side of aortic arch (beginning of aorta as it leaves heart)
o runs dorsal to bifurcation of trachea (branching of trachea into two bronchi)
o diverges slightly to left as it runs caudally in mediastinum ventral to aorta
o penetrates oesophageal hiatus of diaphragm (muscular structure separating thorax from abdomen)

16

abdominal segment of the oesophagus where is it located and what does it follow

very short, especially in ruminant
once goes past diaphragm passes over dorsal border of liver (indenting it) to join the stomach dorsally at the cardia

17

describe the structure of the mucosa of the oesophagus

thrown into prominent longitudinal folds, thus great dilation of tube possible - expansion of oesophagus
composed of 2-3 layers-
1) Epithelium stratified squamous - keratinised or non-keratinised, depending on species (depends on consistency of ingested food -usually keratinised in horse, ruminant and pig but not in carnivore - eating less traumatic substances less likely to damage lining of oesophagus)
2) Lamina propria - connective tissue layer
rich in collagen and elastic fibres; leucocytes; ducts of submucosal glands
3) Muscularis mucosae - in some cases thin layer of smooth muscle in mucosa at caudal end of oesophagus usually absent at cranial end (subject to species variation)- provides localised movement of mucosa

18

describe the structure of the submucosa layer of the oesophagus

Loose connective tissue, mainly collagen and some elastic fibres
- rich in glands - produce mucus for lubrication - secretory cells like similar to mucus secreting cells in salivary glands
- contains glands at cranial end in most species (but along full length of oesophagus in dog

19

describe the structure of the muscularis externa layer of the oesophagus - what types of muscle for different species

-muscle layer which moves food into stomach by contraction
-cranial and caudal oesophageal sphincters (constrict and stop movement of food through oesophagus at either end) suggested capable of maintaining intra-oesophageal intraluminal pressure higher than intra-gastric pressure.
- The caudal "sphincter" in the horse has sufficient tone that it usually remains closed during gastric dilation to the point of gastric rupture without vomiting occurring.) - horses unable to vomit
-Usually thickest layer of wall - Two layers of muscle - difficult to define at cranial end, but at caudal end obvious inner circular and outer longitudinal layers
- dog and ruminant- composed of skeletal muscle throughout; other species usually skeletal at cranial end - becomes smooth at caudal third in herbivores

20

describe when the adcentitia and serosa are present in the oesophagus and what it is

Adventitia - where oesophagus lies outside thorax and abdomen; connective tissue merges with that of surrounding structures
o Serosa - where oesophagus lies within thorax or abdomen; connective tissues covered by epithelial layer - just a cavity surrounding

21

blood and nerve supply to the oesophagus

Blood supply
• branches of common carotid, bronchoesophageal and left gastric arteries, depending on region
Nerve supply - autonomic
• branches of sympathetic and parasympathetic (vagus 10th cranial) nerves

22

list the sites of possible obstruction in the oesophagus

1) Cranial and caudal oesophagus
2) Entrance to thoracic cavity - thoracic inlet
3) Over base of heart
4) Immediately anterior to diaphragmatic hiatus

23

differences of the oesophagus in birds

o oesophagus is located on right side of neck in cervical region.
o crop - a saccular diverticulum (out pocketing) of oesophagus cranial to thoracic inlet.

24

defence mechanisms in the oral cavity

1) saliva
2) resident flora
3) secreting immunoglobulins
4) phagocytes and offer effector cells
5) high rate of epithelial turnover
6) lysozyme and secretory phospholipase
7) taste buds that potentially reject toxic material based on taste and feel

25

colour change of oral mucosa and possible reasons

black - normal melanin with age or melanoma
yellow - jaundice
white - anaemia
blue/purple - cyanosis - decreased venous drainage - heart disease
red - inflammation
brown - systemic problems

26

list the two types of facial clefts and why they occur and results of this abnormality

failure of fusion during embryogenesis
Include cleft palate (palatoschisis) and cleft lip/hare lip (cheiloschisis) usually occur together.
Palatoschisis is due to failure of closure of the lateral palatine processes of the maxillary bones.
Important sequelae to the host are starvation due to inability to create a negative pressure in the mouth and resultant failure to suckle - generally when noticed and aspiration pneumonia (no effective separation between nasal and oral cavity).

27

what is
Brachygnathia - inferior
Brachygnathia – superior
Agnathia

short mandible “parrot mouth”. Top jaw overriding the bottom jaw. Occurs in cattle, sheep, horses and dogs.
short maxilla. Heritable in dog, swine and cattle breeds. Progressive with age
absence of mandible. Most common in lambs, usually associated with other facial abnormalities

28

define stomatitis, glossitis, gingivitis, cheilitis, pharyngitis

stomatitis = diffuse inflammation of the oral cavity
Glossitis - inflammation of the tongue
Gingivitis - inflammation of the gingiva
Cheilitis - inflammation of the lips
Pharyngitis - inflammation of the pharynx

29

define erosions, ulcers, vesicle, papule, granuloma

Erosions: partial loss of epithelium, forming a shallow indentation - doesn't extend into lamina popria - most superficial of the lesions
Ulcers: full thickness loss of epithelium forming a deep indentation - in through basement membrane into submucosa and lamina popria
Vesicle: A thin walled, raised, fluid-filled lesion, typically above basement membrane - can easily rupture and appear as a erosion which may become an ulcer - soft white to pink in colour, hard to find
· Papule: raised flat topped lesion
· Granuloma: collection of macrophages often surrounding a necrotic centre (inflammation)

30

clinical signs of oral cavity inflammation

· anorexia
· hypersalivation (ptyalism)
· bad breath (halitosis)
· reddening, swelling, exudates affecting the oral tissues (indicating inflammation)
· ulcers, erosions, masses