Chapter 4 Tissue Level of Organization

Professor Alonge・2 minutes read

Tissues are groups of cells with specific functions connected by cell junctions, classified into categories like epithelial, connective, muscle, and nervous tissues. The text discusses cell junctions, tissue classification, and the importance of different types of tissues in the body.

Insights

Cell junctions are connectors between cells that serve specific functions, with tight junctions preventing material passage, gap junctions allowing nutrient and signal movement, and desmosomes connecting cells under stress.
Tissues are classified into four types: connective, muscle, epithelial, and nervous tissues, each with distinct functions and characteristics, such as epithelial tissues covering surfaces and glands, and muscle tissues contracting and relaxing.
Connective tissues are further categorized into proper, supportive, and fluid types, with grand substances like water, polysaccharides, and proteins playing essential roles in binding cells, providing support, and facilitating nutrient and gas transportation within tissues.

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Recent questions

What are the main types of tissues?
Connective, muscle, epithelial, nervous tissues.

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Summary

00:00

Cell Junctions and Tissues: A Brief Overview

Tissues are groups of cells working together with a specific function, connected by cell junctions.
Cell junctions are connectors between cells for specific functions.
Cytology studies individual cells, histology studies tissues, and pathology studies diseases affecting tissues.
Biopsy studies living tissue samples, while autopsy studies tissues from deceased individuals.
Cell junctions come in three types: tight junctions, gap junctions, and desmosomes.
Tight junctions are tight connections preventing material passage, found in areas like the urinary bladder.
Gap junctions allow nutrient and signal movement between cells, found in areas needing electrical signal conduction.
Desmosomes use cell adhesion molecules to connect cells under stress, found in areas like the skin and intestines.
There are four types of tissues: connective, muscle, epithelial, and nervous tissues.
Epithelial tissues cover surfaces and make glands, lacking a vascular system and undergoing mitosis for renewal.

21:22

Cell Classification and Epithelium Layers Explained

SEO stratify refers to a building that appears tall from the outside but is actually a single-story structure with high ceilings inside.
The classification of cells based on shape includes squamous cells, which are flat, cuboidal cells with similar length and breadth, and columnar cells that are tall and slender.
Transitional cells in the urinary bladder can change shape from cuboidal to flat based on bladder fullness, adapting to their function.
Stratified epithelium is named based on the cells at the apical surface, with simple epithelium having one layer of flat, cuboidal, or columnar cells.
Simple squamous epithelium is found in the kidney and lungs, reducing friction and aiding in absorption and secretion.
Simple cuboidal epithelium, found in the thyroid gland, provides protection, secretion, and absorption functions.
Simple columnar epithelium, seen in the gallbladder and intestines, protects, secretes, and absorbs substances.
Pseudostratified columnar epithelium appears to have multiple layers due to varying nucleus positions but is actually a single layer attached to the basement membrane, found in the respiratory tract.
Stratified epithelium has multiple layers, with stratified squamous epithelium found in skin and mucous membranes for protection against abrasion and pathogens.
Stratified columnar epithelium has topmost cuboidal cells, while stratified cuboidal epithelium has topmost columnar cells, with the name determined by the cells at the apical surface.

40:07

Cell Types and Gland Functions in Tissues

Cells in tissues are named based on their appearance on the surface, not on the lower part.
Columnal cells are found in the basement membrane, while Kua cells are not considered for naming.
Transitional cells change shape in the urinary bladder when empty or full.
Glandular cells can be exocrine or endocrine, with exocrine glands needing a duct to secrete their products.
Exocrine glands, like sweat glands, secrete products that need a duct for transportation.
Endocrine glands, like the thyroid gland, secrete products directly into the blood without needing a duct.
Exocrine glands can be unicellular, multicellular, simple, compound, tubular, or branched.
Compound glands can be tubular, acinar, or tubuloacinar, found in mammary glands or respiratory systems.
Glands can function as merocrine, apocrine, or holocrine, releasing products differently.
Connective tissues are divided into proper, supportive, and fluid types, with examples like bone, blood, and cartilage.

59:23

Grand Substances: Functions and Types in Tissues

Grand substances consist of water, polysaccharides, and proteins.
Examples of grand substances include polysaccharides like GAG (glucose amino glycans).
Grand substances are found between cells and fibers, varying in consistency from fibrous to solid.
Their functions include binding cells, providing support, and acting as a medium for nutrient and gas transportation.
Connective tissues are classified into embryonic and mature types.
Embryonic connective tissues originate from mesoderm cells and are present in embryos and fetuses.
Arular tissues are widely distributed and consist of fibroblasts, hardocytes, and blood cells.
They contain collagen, elastic, and reticular fibers, each with distinct characteristics.
Adipose tissues store fat, provide energy, prevent heat loss, and protect organs.
Reticular tissues provide support to cells and form complex three-dimensional structures in organs like the kidney and liver.

01:20:01

Bone Structure and Muscle Tissue Overview

Osto site is like a shell with the hocy inside, connected to the central Canal through canaliculi.
Canaliculi are canals connecting every launer to the central Canal for nutrient exchange.
Lamela are concentric rings around the central Canal inside the host, composed of calcium and phosphate.
Compact bone is found at the outer portion of bones, with epiphysis, metaphysis, and diaphysis making up different parts.
Diaphysis, also known as the shaft, is composed of compact bone arranged in basic units called oan.
Canaliculi allow cytoplasmic extension of the hosto side to reach other osto sides for nutrient exchange.
Cartilage cages are precursor cells for bone cells, embedded in an extracellular matrix with fibers and condrin sulfate.
Three types of cartilage are hyaline, fibrocartilage, and elastic cartilage, with fibrocartilage being the strongest due to its fiber composition.
Fibrocartilage is found in weight-bearing areas like the knee joint, between pelvic bones, and vertebral bones.
Muscle tissues are made up of muscle fibers that contract and relax, with skeletal muscles being voluntarily controlled by the somatic nervous system.

01:39:01

Neurons and Neuroglial Cells in Tissue Repair

Neurons are the primary cells in neural tissue, with neuroglial cells serving as supporting cells, with about 10 neuroglial cells for every neuron.
Neuroglial cells solely support and nourish neurons, providing physical structure, repairing tissue framework after injury, and regulating the composition of interal fluid surrounding neurons.
Tissue repair varies among different tissues, with some like epithelial cells constantly replacing themselves, while nerve cells have slow regeneration depending on the location of damage.
Factors affecting tissue repair include diet, blood circulation, and age, with good blood circulation and proper nutrients crucial for faster healing, while aging reduces the ability of tissues to repair.

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