User:Yanping Nora Soong/M1/exam 3

General tissue organization (review)

Exocrine glands

Organization

Glandular organization

• Tubular gland
• Acinar gland (sac-like)

Ductal organization

Branced/compound v. simple

Method of secretion

Note: taken ad verbatim from exocrine gland. Will resumnmarize later

• Merocrine – the cells of the gland excrete their substances by exocytosis into a duct; for example, pancreatic acinar cells, maximum sweat glands of humans, salivary glands, goblet cells, intestinal glands, tear glands, etc.
• Apocrine – the apical portion of the cytoplasm in the cell membrane, which contains the excretion, buds off. Examples are sweat glands of arm pits, pubic region, skin around anus, lips and nipples; mammary glands, etc.
• Holocrine – the entire cell disintegrates to excrete its substance; for example, sebaceous glands of the skin and nose, meibomian gland, zeis gland, etc.

Product secreted

Note: taken ad verbatim from exocrine gland. Will resumnmarize later

• Serous cells secrete proteins, often enzymes. Examples include gastric chief cells and Paneth cells
• Mucous cells secrete mucus. Examples include Brunner's glands, esophageal glands, and pyloric glands
• Seromucous glands (mixed) secrete both protein and mucus. Examples include the salivary glands: although the parotid gland (saliva secretion 25%) is predominantly serous, the sublingual gland (saliva secretion 5%) mainly mucous gland, and the submandibular gland (saliva secretion 70%) is a mixed, mainly serous gland.
• Sebaceous glands secrete sebum, a lipid product. These glands are also known as oil glands, e.g. Fordyce spots and Meibomian glands.

Gastrointestinal

Anatomy overview

Enteric ganglia

As an ensemble, rivals the CNS in mass ("the second brain").

• Auerbach's plexus
• Meissner's plexus

Histology (general pattern)

General histological organization diagram

• Mucosa

• Epithelium
• Lamina propria
• Muscularis mucosa

• Submucosa

• Meissner's plexus

• Muscularis propria

• Circular muscle
• Myenteric plexus
• Longitudinal muscle

• Serosa or adventitia

Generalized cell types

• Enteroendocrine cell

Oral cavity and mucosa and esophagus

The muscularis propria (muscularis externa) of the top 1/3 of the esophagus is skeletal muscle, not smooth muscle. The bottom 1/3 (preceding the gastroesophageal junction) is smooth muscle only. The middle 1/3 is mixed.

• Oral mucosa
• Gastroesophageal junction (review histology)

Stomach

General organization

The stomach has three smooth muscular layers, adding an exception to the pattern:

• Inner circular smooth muscle
• Middle oblique smooth muscle (a "deep inner" layer)
• Outer longitudinal smooth muscle

Generally, the epithelium of the stomach "pits" into the lamina propria, where various stomach glands are located. There are regional differences between the 1) cardia 2) pylorus) and 3) stomach body

Gland histology

Fundus glands

• Gastric chief cells (zymogenic cells) are rich in endoplasmic reticulum (staining basophilic - likely for ribosomal RNA and messenger RNA) facilitating the production of large amounts of pepsinogen]
• Parietal cells stain eosinophilic (due to abundance of mitochondria) and produce stomach acid (hydrochloric acid) and cobalamin-binding intrinsic factor (which protects vitamin B12 from degradation until it can be "unwrapped" and absorbed in the ileum

• Parietal cells can be recognized by their intracellular canaliculus

Small intestine

Brunner's glands

General organization

• Circular folds start in the duodenum (3-5 cm from the pylorus), are abundant in the jejunum and are almost absent in the ileum.
• The microvilli in villi are dense in non-motile actin projections (vertical and horizontal) linked by fimbrin, capped by villin underneath the cell membrane

Broadly distributed cells

• Paneth cells
• Goblet cells
• Enterocytes
• Enteroendocrine cells

Enterocyte absorption physiology

• Proteins are broken up into peptide fragments and amino acids via pancreatic proteases in the lumen of the small intestine. The free amino acids and peptides are imported into the apical portion of the enterocyte via apical surface (brush border) via peptide transporter 1 (cotransported with H+) and sodium-dependent amino acid transporters. Peptides should be 2-3 AA long; any longer than 4 AA will not be imported.
• Imported into the bloodstream via basal surface amino acid and peptide transporters

Duodenum

• Brunner's glands (submucosal! other than the esophagus, which lack villi, unique to the duodenum)

Large intestine

Appendix

• Many lymphoid aggregates - dominated by lymphoid tissue