Lecture 4 - Basic tissues Flashcards
Epithelia: what is it, where is it located, and what are its important characteristics?
Loosely-packed cells supported by a basement membrane
Cover surfaces, line cavities, and tubules, and form glands
Has avascularity (few or no blood vessels), good regeneration, polarity (apical, basal), apical always faces out of the body or into a lumen while basolateral faces the internal body
How many layers is simple epithelium?
One
How many layers can stratified epithelium be?
Two or more
Squamous, cuboidal, columnal (in terms of shape)
Flat, cuboidal, and rectangular
Types of epithelia (6)
- Simple squamous,
- Keratinised stratified squamous,
- Non-keratinized stratified squamous,
- Simple cuboidal,
- Simple columnal,
- Pseudostratified stratified columnar with goblet cells .
Keratinized stratified epithelia: what is it, what does it do, where is it mostly present?
Many layers of flat cells with oval-shaped nuclei containing keratin
Specially structured to be waterproof and reduce evaporation from underlying tissues
Epidermis (external skin)
Pseudostratified ciliated columnar with goblet cells: what is it, what does it do, where is it mainly found, and any special characteristics?
Columnar cells seemingly structured in layers, but are in fact all connected to one basement membrane.
Mucociliary escalator
Trachea and large airways
Contain goblet cells (secrete mucus and mainly mucin glycoproteins) and cilia (slender, microscopic, hair-like structures or organelles that extend from the surface of some cells).
Goblet cells: what are they, where are they mainly found, and what is their main function?
A type of intestinal mucosal epithelial cell, which serves as the primary site for nutrient digestion and mucosal absorption.
They are mainly found throughout digestion system, as well as the nose and throat
The primary function of goblet cells is to synthesize and secrete mucus. As the primary secretory cell in the superficial epithelium of large airways, goblet cells secrete mucin glycoproteins, the major macromolecular components of mucus.
Simple squamous epithelium: what is it, what does it do, and where is it mainly found?
One layer of flat cells with oval-shaped nuclei
Exchange of material: gases and nutrients
Blood vessels and alveoli
Non-keratinised stratified squamous epithelium: what is it, what does it do, and where is it mainly found?
Many layers of flat cells with oval-shaped nuclei not containing keratin
Protection / forming a barrier
Oral cavity, oesophagus
Simple cuboidal epithelium: what is it, what does it do, and where is it mainly found?
One layer of square cells with round-shaped nuclei
Secretion and absorption
Glands and kidney tubules
Simple columnar epithelium: what is it, what does it do, where is it mainly found, and any special characteristics?
One layer of rectangular cells with oval-shaped nuclei located basally
Secretion and absorption
Gastrointestinal tract
Contain microvilli
Intercellular junctions: what are they and what are their examples?
Things that bind cells together
Desmosomes, hemidesmosomes, tight junctions, and gap junctions
Desmosomes: what are they, what are they made of, and what do they do?
Very strong connections between adjacent cells,
Desmoplakin and other proteins
Resist stretching and twisting
Hemidesmosomes: what are they, what are they made of, and what do they do?
Attach cells to the base membrane
Several membrane-spanning proteins
Acts as an anchor to the underlying tissue and stabilises the cell’s position
Tight junctions: what are they and where are they, what are they made from, and what do they do?
Interlocking proteins that bind cells together near the apical edge
Transmembrane proteins and cytoplasmic scaffolding proteins
Prevent the passage of water and solutes between cells
Gap junctions: what are they, what do they do, and what are they made of?
Interlocking membrane proteins containing a central pore, binding cells together and allowing the movements of small molecules and ions (mainly found in cardiac muscle)
Channel proteins: connexions (vertebrates) and innexins (invertebrates)
Connective tissue: its functions
- Forms a structural framework for the body
- Supports, surrounds and interconnects other tissue types
- Protects delicate organs
- Transports fluids and dissolved materials
- Stores energy reserves
- Defends body from microorganisms
Connective tissue: what cells are present, what does the EM consist of, and what are the types?
An extracellular matrix surrounding cells, including mainly fibroblasts, adipocytes, macrophage, and mast cells
Consists of the ground substance, tissue (extracellular) fluid, and fibres; collagen, reticular & elastic
The two types of CT are specialised connective tissue and connective tissue proper
Fibroblasts
Secrete collagen proteins that help maintain the structural framework of tissues.
Adipocytes
Acts as a calorie storage system accepting chemical energy in the form of glucose and fatty acid from the blood and converting these metabolites to trigylcerides for storage during fed conditions via lipogenesis.
Macrophages
Specialised white blood cells involved in the detection, phagocytosis and destruction of bacteria and other harmful organisms. In addition, they can also present antigens to T cells and initiate inflammation by releasing molecules (known as cytokines) that activate other cells.
Mast cells
Play an important role in innate and adaptive immunity. Mast cells recognize harmful antigens by binding to pathogens directly or associating with Pathogen-Associated Molecular Patterns (PAMPs) on the mast cell surface
Specialised connective tissue: the three types
Bones, blood, and cartilage
Connective tissue proper: the three types
Loose areolar, dense regular, and dense irregular
Loose areolar: what is it, what does it do, what does it contain, and where can you find it?
Cellular connective tissue with thin and relatively sparse collagen fibers
Loose connective tissue works to hold organs in place
Contains lots of ground substance, few fibres (collagen & elastic), and a variety of cells: fibroblasts, adipocytes, and macrophages (transient)
Found under the epithelium that covers and lines the body surfaces
Dense irregular: what does it do, how does it do it, what does it contain, and where can you find it?
Provides strength to the skin,
Resists tearing by excessive stretching and distension
Little ground substance, many collagen fibre bundles arranged haphazardly, few cells (mainly fibroblasts)
Found in the dermis
Dense regular: what is it, what does it do, what does it contain, and where can you find it?
White, flexible tissue that contains tightly packed bundles of collagen fibres running in one direction, arranged parallel to the direction of forces exerted on the particular body part where the tissue is located.
Connects bones to things and transfers forces to the bones
Contains little ground substance, many densely packed bundles of collagen fibres arranged in parallel rows, and few cells (mainly fibroblasts)
Found in tendons and ligaments
Ground substance: what is it in connective tissue?
An amorphous gelatinous material. It is transparent, colourless, and fills the spaces between fibres and cells. It actually consists of water and large molecules (glycosaminoglycans (GAGs)) which link together to form even larger molecules called proteoglycans.
Dermis: what is it, where is it located?
It’s a fibrous structure composed of collagen, elastic tissue, and other extracellular components that include vasculature (vessels and lymph), nerve endings, hair follicles, and glands.
It’s sandwiched between the epidermis and subcutaneous tissue.
Subcutaneous tissue: what is it where is it located
It is the deepest skin layer, composed of fat cells, collagen, blood vessels, and nerves
Located underneath the dermis and is the third layer of the skin.
Three types of muscle tissue and their similarities
Skeletal, smooth, cardiac
Elongated parallel to the axis of contraction, contain many mitochondria and contains contractile elements
Skeletal muscle: what does it do and where is it found, any key features, and what nervous system affects it?
Moves and stabilises the skeleton, also involved in respiration
Attached to bones and forms sphincters (a ring of muscle surrounding and serving to guard or close an opening or tube) in digestive and urinary tracts.
Long and cylindrical, multi-nucleated, and striated
Somatic nervous system
Smooth muscle: what does it do and where is it found, any key features, and what nervous system affects it?
Gastrointestinal movement (peristalsis), alters the diameter of airways and blood vessels
Walls of organs, blood vessels, and airways
Short, fusiform (tapering at both ends; spindle-shaped) cells with one centrally located nucleus, non-striated
Autonomic nervous system
Cardiac muscle: what does it do and where is it found, any key features, and what nervous system affects it?
Helps to circulate blood and maintain blood pressure
Located in the heart wall
Branched, striated muscle fibres with the cells having intercalated discs with each having one to two central nuclei
Autonomic nervous system
Intercalated discs: what are they, what do they do, and what is their function?
Part of the cardiac muscle sarcolemma
Contain gap junctions for depolarization between muscle fibres and desmosomes that hold the fibres together during cardiac muscle contraction
Ensures the cardiac muscle work as a single unit
