Salivary Glands

Parotid

 amylase (ptyalin)

 1 - 4 hexose linkages

Submaxillary & Sublingual

mucin (protein for lubrication)

Salivary Glands

Acinus type glands:

Primary secretion by secretory cells and then modified by duct cells as saliva passes through on the way to the oral cavity

Saliva

As saliva flows down duct:

[Na+] and [Cl-] decrease

[HCO₃-] and [K+] increase

As flow rates increase, this exchange is less complete

Salivary pH

Saliva pH is basic (vs. plasma pH)

WHY??

Consider Ca⁺⁺ in teeth

Excitatory Signal Molecules

ACh from Parasympathetic NS onto muscarinic receptors

VIP from enteric NS

Increased blood flow in response to kininogen activation

Kininogen Activation

Glands release Kallikrein when activatedPlasma globulin

Results in peptide --> bradykinin

Bradykinin ---> local vasodilation (10X increase in BF)

Other Components of Saliva

Muramidase --> cleave muramic acid in bacterial cell walls

Lactoferrin --> binds Fe⁺⁺

Epidermal growth factor --> stimulates mucosal cell growth

IgA

Lingual lipase (small amounts)

ABO antigens (secreters)

Regulation of Salivary Secretion

Cephalic Phase

Oral Phase

Gastric Phase

Vagal - vagal reflex

Enteric, Sympathetic, & Parasympathetic NS

Smooth Muscle & Structure of Gut

Stomach

Figures 20 - 1 through 4

Innervation of GI Tract

Parasympathetic

Sympathetic

Enteric

local, intrinsic neurons

cell bodies in ganglia in GI walls

integration

See Figs 20-2

Enteric Nervous System
Figs 20 - 2 & 19

Receptors

Mechano

Chemo

Thermo

Interneurons

Reflexes & ‘motor’ programs

Excitatory and Inhibitory motor neurons

Muscles

Blood vessels

Secretory cells

Enteric Nervous System

Vagus nerve contains afferent and efferent neurons to connect enteric n.s. with cns

Activity of enteric n.s. influenced by:

chemical composition

volume

Autonomic inputs

Sympathetic Actions

Inhibition:

decreased NT release by enteric system via ₂ on presynaptic terminals

Parasympathetic

Excitation:

ACh on muscarinic receptors

directly onto muscle and secretory cells

directly onto enteric nerves to cause epsp’s

Smooth Muscle:
Chapter 12; pages 348 - 355

Linked by gap junctions

Membrane invaginations - caveoli

Little SR

Actin & Myosin but no striations

Intermediate filaments

Smooth Muscle

Oscillating Vm

High G_Na+ and variable G_K+

Responds to stretch

Mysoin regulation of contraction

Ca⁺⁺ for Contraction

Open membrane channels

Voltage gated membrane cannels

Ligand gated membrane channels

SR and ER

Released by IP₃

Ca⁺⁺ Removal

SR, ER, & Membrane Ca⁺⁺ ATPase

Na⁺ - Ca⁺⁺ exchange in membrane

STOMACH

Stomach Mucosal Surface: Folds are called Rugae gastricae

Gastric Glands

Cardiac

mucus producing columnar cells

Pyloric

mucus and G cells producing peptide hormone gastrin

Oxyntic

Oxyntic Glands

Surface Epithelium - insoluble mucus

Neck Cells - soluble mucus

G cells - gastrin

Parietal (or oxyntic) Cells - HCl & Intrinsic Factor

Chief Cells - pepsinogen