Lecture 30: Upper GI

Question 1

Describe he histology of the lip

Answer 1

The lip is composed of a core of skeletal muscle (obicularis oris) cells embedded in FECT and covered externally by skin. [transition pt. Btw skin and mucosa]

Cheek is similar to lip.

Question 2

Describe the mucous membrane lining the oral cavity

Answer 2

Oral cavity is lined w/ a mucous membrane lying on a vascular FECT layer. Mucosa consists of :

• stratified squamous epithelium
• basement membrane
• lamina propria-mixed mucous glands.

Internal poorly keratinized, modified stratified squamous epithelium on top of lamina

Question 3

List the 3 structures derived from the epithelial bud

Answer 3

Ectoderm: forms enamel organ-formed under influence of mesoderm and neural crest

Neural crest
And
Mesoderm: give rise to dental papilla-dentin, cementum and pulp

Question 4

Discriminate btw the dental papilla and the enamel organ w/ regard to their embryonic origin and their derivatives.

Answer 4

Enamel organ derived from ectoderm

Dental papilla dervied from neural crest and mesoderm

Question 5

What is the dental lamina?

Answer 5

Dental primordium is formed from basal cells of the oral ectoderm. The labiodental lamina is an epithelial shelf that grows from the thickened primordium into the mesenchyme as a bifid structure. The external limb splits later to form a groove that depends to separate the lip and the remainder of the mouth. The internal limb- beginning development of the tooth.

Question 6

Describe the histology and specific functions of the odontoblasts, ameloblasts, and cementoblasts

Answer 6

odontoblasts: form dentin matrix throughout the lifespan of the tooth-single layer of cells line the pulp cavity. Each cell produces extension=tomes’ dentinal fibers: this is what gives rise to the present in->dentin. Increment lines (of ebner and owen)
ameloblasts: form enamel. Only on tooth crown. 96% inorganic salts…hardest substance in body. Laid down in prisms. Each prism is formed by one ameloblast. Tomes’ processes: secreting apical domains. Increment lines of retains are periods of rhythmic growth.
cementoblasts: cells of dental differentiate into cementoblasts deposit cementum on the dentin of the root from neck to apex

Question 7

Describe the histology and functions of the periodontal membrane.

Answer 7

CT tissue layer from dental sac w/ fibroblasts, osteoblasts, etc.

• highly metabolic active tissue.
• binds cementum to bony socket.
• sharpens fibers extend from cementum to alveolar wall via the membrane.
• limited movement
• absorbs pressures of mastication and prevents this pressure from damaging alveolar bone.
• affected by diseases:scurvy, diabetes

Question 8

What is the sulcus terminalis?

Answer 8

Separates anterior 2/3 of upper oral potion and posterior 1/3.

Question 9

List and compare the 4 kinds of lingual papillae.

Answer 9

1. filiform papillae: most numerous, even distribution, lack taste buds.increase roughness of surface of tongue to move food.
2. fungiform papillae: relatively few, mushroom appearance, taste buds present on oral surface.
3. foliate papillae: rudimentary in humans, not in other animals. Pharyngeal portion is free of papillae but contains lingual tonsils.
4. circumvallate papillae: along sulcus terminalis as projections surrounded by moat. Tastebuds on lateral walls, ducts of von ebners glands (serous) open to moat

Question 10

Describe the structure of taste cells.

Answer 10

Bud: Contain 2 types of cells derived from a single stem cell.

Each cell is long and slender w/ elongated central nucleus and terminates as a short taste hair which projects into the external opening celeb the outer taste pore. Apical microvilii w/ taste receptors. Basal part of cell releases neurotransmitters. Taste cells distributed btw supporting cells.

Question 11

List and give general characteristics for each of the 4 layers of the gut tube, including the nerve plexuses and the lymphoid tissue.

Answer 11

1. mucosa (innermost): secretory, absorptive, protective functions. Loose areolar CT in lamin propria- w/ glands and GALT. Also has 1-3 layers of smooth muscle
2. submucosa: meissner’s plexus, vascularized, dense irregular CT
3. muscularis externa: inner circular layer of smooth muscle. Myenteric (Auerbach’s) nerve plexus lies btw the 2 layers of muscle tissue.
4. outermost layer: dense irregular CT. Serosa forms the visceral peritoneum.

GALT=IgA specialized squamous epithelial cells (M cells) in gut lumen serve to transport food antigens to lymph follicles. Antigen-stimulated B cells in follicle secrete IgA