Human Digestive System: Anatomy and Physiology
Gastrointestinal Tract Structure
- Serosa: Connective tissue and peritoneum.
- Muscularis: Two layers of muscle (inner circular, outer longitudinal) and the myenteric plexus (ENS).
- Submucosa: Dense connective tissue, glands in the lamina propria, and submucosal nerve fibers regulating glandular activity.
- Mucosa: Mucous epithelium with columnar cells and microvilli.
GI Tract Functions
Functions include motility, secretion, digestion, absorption, and excretion. The process follows: Food/water → Bolus →
Read MoreDiabetes Mellitus: Clinical Diagnosis and Management
Chronic Complications of Diabetes Mellitus
Pathogenesis: Chronic hyperglycemia leads to the formation of Advanced Glycation End-products (AGEs), Protein Kinase C (PKC) activation, increased Reactive Oxygen Species (ROS), and the polyol pathway. These processes result in endothelial dysfunction, basement membrane thickening, and both microvascular and macrovascular damage.
Microvascular Complications
- Retinopathy: Non-proliferative (microaneurysms, hemorrhages, cotton-wool spots, macular edema) and Proliferative
Key Functions in Human Biology
Digestive and Metabolic Functions
1. Saliva and Stomach Acid
- Saliva: Lubricates food for swallowing, moistens the mouth, and contains the enzyme Salivary Amylase (Ptyalin) which begins the digestion of carbohydrates (starches).
- HCl (Hydrochloric Acid): Maintains an acidic pH (1.5–3.5) in the stomach to activate pepsinogen into pepsin (for protein digestion) and kills ingested bacteria/microbes.
2. Basal Metabolic Rate (BMR)
- BMR: The minimum amount of energy (calories) required by the body to maintain
Pharmacology Concepts: Drugs, Receptors, and Signaling
Parasympathomimetics
Definition
Parasympathomimetics are substances that mimic the effects of the parasympathetic nervous system, stimulating cholinergic receptors.
Classification
- Direct-acting: Cholinergic agonists (e.g., acetylcholine, pilocarpine)
- Indirect-acting: Cholinesterase inhibitors (e.g., neostigmine, physostigmine)
Acetylcholine Pharmacology
Mechanism
- Muscarinic receptors: Stimulates smooth muscle contraction, glandular secretion.
- Nicotinic receptors: Stimulates muscle contraction, ganglionic
Mechanisms of Synaptic Transmission and Plasticity
The Process of Synaptic Transmission
The action potential signal arrives at the axon terminal (the bouton). The local depolarization causes Ca channels to open. (Is this channel voltage, chemically, or mechanically gated? Voltage). Ca enters the presynaptic cell because its concentration is greater outside the cell than inside. The Ca, by binding with calmodulin, causes vesicles filled with neurotransmitter to migrate towards the presynaptic membrane.
Neurotransmitter Release and Exocytosis
The vesicle
Read MoreBioassay and Clinical Endocrine & Cardiac Concepts
Bioassay
Bioassay is defined as the estimation of the potency of an active principle in a unit quantity of a preparation.
• Detection and measurement of the concentration of the substance in a preparation using biological methods.
Importance of Bioassay
Bioassays, as compared to other methods of assay (e.g., chemical or physical assay), are very important because they are the only method of assay if:
- Active principle of a drug is unknown or cannot be isolated (e.g., insulin, posterior pituitary extract)