Epithelial, Connective, Muscle, and Nervous Tissues: An Overview
Epithelial Tissue
Epithelial tissue lines the body’s exterior and internal surfaces of hollow organs, including those of the respiratory, digestive, urinary, and reproductive systems. Its primary function is protection and selective barrier formation, regulating substance passage. This non-vascularized tissue receives nutrients via diffusion from adjacent vascularized tissue.
Glandular Epithelial Tissue
During embryonic development, some epithelial cells specialize in secretion, forming glands. These
Read MoreSmooth Muscle Pharmacology and Drug Interactions
Smooth Muscle Relaxation
Increasing cAMP or cGMP → PKA or PKG → phosphorylation of MLCK or phosphorylation of VOCCs. This phosphorylation prevents MLCK from phosphorylating MLC (reducing the amount of phosphorylated MLC) → ↓ [Ca2+] → This is a powerful “anti-contraction” mechanism → relaxation.
Smooth Muscle Contraction
Release of Ca2+ from intracellular stores → calcium-calmodulin complex. This activates myosin light chain kinase (MLCK), leading to phosphorylation of MLC (myosin light
Epithelial Cell Junctions and Specializations
Apical Specializations
Microvilli
Microvilli are cylindrical, membrane-bound cytoplasmic extensions that increase the absorptive surface of cells without increasing cell volume. They are abundant in organs involved in substance exchange. A collection of microvilli is called a brush border. Microvilli are classified into two types based on their arrangement: orderly and disorderly (or accidental). They have a diameter of 0.1μm and a length of 0.6 to 0.8μm, observable with electron microscopy.
Read MoreContraceptive Methods: A Comprehensive Guide
Contraceptive Methods
Introduction
Birth control methods prevent or reduce the likelihood of pregnancy. These methods involve various actions, devices, or medications, each with varying effectiveness.
Permanent Methods
Sterilization
Male Sterilization
This involves cutting or tying the vas deferens, which prevents sperm from traveling from the testicles to the penis. This procedure does not affect sexual function or hormones.
Female Sterilization
This involves cutting or tying the fallopian tubes, preventing
Read MoreClassification of Invertebrate Animals: A Comprehensive Guide
Classification of Invertebrate Animals
Diploblastic Animals
Sponges
Sponges are primarily marine animals that live attached to surfaces in salt water. They vary in size and have a skeleton made of secreted substances (spicules) which can be silica, calcium carbonate, or spongin. Their bodies have channels and folds where water carrying nutrients circulates. Inside, a substance called mesoglea contains specialized cells called amebocytes that collect food. Sponges obtain food directly through pores
Read MoreGenetics: A Comprehensive Overview from Classical to Molecular Concepts
Concept of Genetics
Genetics, the science of biological inheritance, studies genes and their expression in organisms. Early studies by Mendel on pea plants revealed patterns of inheritance through crosses and statistical analysis of offspring. The 20th century saw the development of classical or Mendelian genetics, based on key principles:
- The unit of heredity is called a gene.
- Genes are transmitted according to defined laws.
- Genes are located on chromosomes.
- Sex is determined by genes on sex chromosomes.