Epithelial Tissue and Cells

Epithelial Tissue

• The human body is constructed from four primary tissue types: epithelial, connective, muscle, and nervous.
• Tissues carry out specific functions through groups of similarly specialized cells.
• Most tissues have cells and extracellular matrix (ECM), which contributes to forming organs.
• Muscular tissue consists of three cell types: skeletal, cardiac, and smooth muscle.
• Nervous tissue is composed of the brain, spinal cord, and nerves.
• Connective tissue includes bone, fat, tendons, and cartilage with abundant ECM and functions to connect disparate tissues/organs.
• Epithelial tissue is composed of adjacent, multi-faceted cells, connected by strong junctions, attached to a thin layer of ECM.
• Sheets of epithelial tissue cover the body’s surface and internal cavities.

Epithelial Cells

• Epithelial cells are found throughout the body on both external and internal surfaces
• Epithelial cells are responsible for passage of material into and out of the body
• Epithelial tissue functions to line, cover, and protect surfaces.
• Absorption occurs as in the intestines
• Glands comprised from secretions such as parenchyma cells.
• Myoepithelial cells are specialized within some epithelial tissues for contraction.
• Sensory cells, such as taste buds or olfactory epithelium, are developed.
• Epithelial tissue rests on the connective tissue, whose boundary is the basement membrane.
• Blood capillaries and nerves are located in the connective tissue; nerves may enter the epithelium.
• Capillaries are not found in the epithelium
• Epithelial cells have polarity due to the unequal distribution of organelles and membrane proteins.
• The basal pole has sections attached to the basal lamina

Apical Pole

• The pole furthest from connective tissue and basment membrane
• This region mediates most of exchanges
• Apical and basal poles have varied functions

Lateral Surface

• Connection point of two adjacent epithelial cells

Basal Lamina

• Separates connective tissue and basal surface by a layer of macromolecules
• Materials received by the receiving epithelial cells are processed through this
• It plays a role in filtration in the kidney glomeruli
• Two layers compose it:

Basal Lamina makeup

• Basal lamina lies closest to the epithelial side under electron microscope
• Reticular lamina is more diffuse

Additional Basal Lamina facts

• Laminin is particular marker within basal surface

Tissue characteristics

• Epithelial cells have connection to each other, and basal lamina, notably within friction susceptible epithelial tissues

Cell-Cell Adhesions

• Tight junctions: occluding junctions located nearest the apical pole; encircle epithelial cells to form the seal
• Adherens Junction: encircle cell in belt shape; actin network of cell contributes to role as cellular skeleton
• Desmosomes are spot-like adhesion with function in cell with support, they don't create belt around cell, desmosomes possess enhanced connection capabilities than either tight junction or adherens injunctions

Gap Junctions

• They mostly communicate across cellular membranes and can happen within different epithelial tissue types

Connexins

• Connexins from other membranes form the passageway for intercellular communication

Microvilli

• Occur in abundant amounts within cellular areas that are destined for intake of materials
• Epithelial cells containing villi occur within surfaces near top regions of cells
• Top sections coated with glycocalyx
• Composed of structural proteins and filaments

Inside Microvilli

• Have actin filaments with connection to each other

Network makeup of terminal villi

• Filament proteins link F-actin to membrane
• In the base of the epithelium, the actin connections connect to intermediate filaments

Stereocilia

• Uncommon apical structure functioning to facilitate absorption with increased surface area
• Occur in male productive channels, sense-oriented interior ear components
• Taller and lower level agility than microvilli

Cilia

• Capable of visualization within apical sections and occur in high proportions along cuboidal as well as columnar cellular regions within epithelial tissue

Flagella

• Appendages taller relative to standard cilia
• Lower amounts
• Classified according functional makeup of component

Functional Makeup - Epithelial Tissue

• Covering
• Glandular
• Organized via shape
• Flattened
• Cuboidal cells
• Columnal

Layer count

• One layer
• Multiple layers
• Tissues consisting flattened cellular regions Are one singular layer thick with dense nuclei.
• For example, Kidney Bowman's capsule and lens are organized of simple epithelium

Simple Cuboidal Epithelium

• Is organized within ducts in kidney thyroid regions
• Cells comprising tissue feature rectangular makeup on base membrane

Simple Columnar Epithelium

• Features rectangular composition within base arrangement of epithelial cells
• Regions of cellular lining often host apical sections characterized by cilia composition

Stratified Epithelium

• Features multiple distinct cell types

Keratinized Stratified Epithelium

• Notably seen within skin, serves body protection against water loss
• Features many desmosomes responsible for production of tight connection that causes irregularly placed nuclei and structural change

Non-keratinized Stratified Epithelium

• Occupies region that does not serve function in water maintenance such as within esophagus, cornea, vaginal canal, mouth.
• Has maintenance in cellular procedure.

Transitional Epithelium

• Possess composition that accommodates shape shift via arrangement of intermediate
• Cuboidal cells in bladders, kidney, urethra
• Provides safeguards against elevated osmotic pressures in specific solutions

Pseudostratified Epithelium

• Tall
• Characterized by location shift
• Is commonly comprised by cilia and is present throughout areas of airway linings.

Secretory Epithelium/Glands

• Typically conduct synthesis, storage and release
• Divided into single and multi layers depending on the arrangement of the organization

Unicellular Glands

• Scattered glandular cells

Goblet cells

• Transmit mucus

Cell clusters

• Hormonal delivery
• Exocrine - delivery throughout epithelial layer

Functionality and structure of different types of glands

• Apocrine gland
• merocrine gland
• holocrine.

Exocrine gland arrangement

• Simple tubular
• Coiled
• Acinar

Structure

• Are surrounded by extracellular matrix but are also bound to cells to allow absorption of materials

Properties of Lumen

• Absors materials and is exposed to outside the tissue

Connective Tissue

• Connective tissue is one of the main tissues.
• The diversity compared with other tissues.
• Contains few cells and the ECM is the main part
• Transports of materials is performed between tissues.

Responsibilities of connective Tissue

• Links up organs
• Supplies the cells in it with nutrition
• Stores nutrients.
• repairs damage.
• defence

Mesoderm

• Gives rise to:
  • cardiovascular system
  • blood cells
  • bone marrow

Ectoderm

• Gives rise to nervous and skin tissue

Endoderm

• Gives rise to digestive tract

Various Connective tissues

• They come from:
  • Mast cells
  • Macrophages
  • Resident Fibrous
  • Adult stem cells

Wandering Connective Tissue

• The source of defence of the immune system,

Origin of cells in connective tissue

• Stem cells that form blood cells

Mesenchymal

• Gives rise to:
  • Fibroblast
  • Basophils
  • Macrophage

Major components of tissue

The most common cell type is the fibroblast that has a elongated nucleus.

Task of those major components

• To produce ECM.

Connective Tissue can be

• Fibroblast for shape can vary
• Fribocyte

Fibroblast has

• A large nucleus
• More irregular edges.

Functions of Macrophage cells

• Engulf and digest dead material
• Release of mediators for inflammatory
• Stimulus.
• Can be found in a variety of places throughout the body with varying names

Mast cells appear

• Oval shape and also surrounded by granules within matrix from dying cells

Plasma cell

• Develops from the multiplication of cell lymphocytes
• Make anti-bodies to neutralise dangers.

Connective Tissue Fibers

• 1.) collagen
  • Are very strong fibers in ECM

Connective Tissue Fibers has subunits

• I. Fibrillar
  • Can exist as fibrils
• II. Sheets and networks
  • Are in form of sheets or networks.
• III. Linking
  • Function as links between components

Type of ground substance

• GAGs
  • Type of glycosaminoglycan
• Protoglycans
  • Amount depend on the amount of glycosaminoglycan
• Glycoproteins
  • Amount depends on the carbohydrate units

Production of matrix and function

• The relative distribution of these elements:
  • Affect properties of tissues

Hydrostatic

• Hydrostatic pushes the compounds through capillaries pushing through liquid into the tissue

Osmotic

• Pressure attracts to albumins pushing through solution

Collagen Fiber

• The most abundant and most present protein in the body consisting of a collection of collagenous components

Elastic Fibers

• Also are part or derived by protein structures

Different Types of Cells

• Resident
• Wandering

ECM

• Extracellular Matrix
  • Collagen Forms strong and thick fibers
  • Reticular Fibers

Cells within the tissue

• Form connection with various molecular components such as sugar based and protein based structures

Cartilage

• Is a type of supportive connective tissue.

Cells

• 1.) Cells -Chondrocytes - chondroblast
• ECM
  • Types of strong fibers
  • Collagen
  • Elastin
  • Glycosaminoglycans
  • Protoglycans. - Are high with sugar which allows them to retain fluid.

Types of Cartilage

• Type: I-III
• Most important fibers are the collagen and also the water.
• Water makes the cartilage resilient to compressions.
• Hyaline The most common version.

Connective Tissue and bone

• They do not have:
  • Nerve tissues
  • Lymph nodes

Important structure for cartilage

• Perichondrium Is a thick sheet surrounding all types of cartilage allowing transfer between cells

Different Types of cartilage from low compression to best compression

• hyaline
• fiborous
• elastic

Composition of hyaline

• Collagen II.
• is high with water allowing diffusion of nutrients from ECM

What all is in hyaline cartilage matrix

• Fibroblast
• Collagen
• Mesenchymal cells
• Chondrioblast
• Chondrocyte

Steps For Bone Formation

• Process happens more within the early stages of life
• Begins with a mesenchymal mass converting into chondroblast

Next Steps

• The cells change to chondrocytes and produce matrix

How to spot on microscope

• All have lucane
• All have some amount of hylaine membrane

Elastic Cartilage

• Features multiple proteins that create elastic structure, along with hyaline fibers

Microscopic Structure View

• Reveals composition of chondrocytes and lack of structural makeup

Components of Fibro cartilage

• Hylaine makeup in line to fibers
• Has composition that forms dense matrix layer

• Bones

• Form for support with support or structure. Also, protection for certain organs. Also is
• 1. Area of production for marrow in early stage of cell production
• Are composed of:
• Osseous 07 matrix
• cells
• bone deposition cells
• bone resorption cells
• Matrix
• A collagen matrix and crystal minerals
• For minerals
• Primarily Calcium and phosphate. For strength
• Type I collagen

•   **Bones cells**
  

• Osteoblasts, osteocyte, osteoclasts, osteogenic cell

What Bones do

• Protect internal structures
• Storage for fats and minerals
• Have important ECM properties
• The functions will involve collagen
• High amount of mineral content
• Calcium Phosphate

Cell Arrangement

• Cells will exist as osteoblast cells
• All bones come of bone marrow

Various Types of Cells

• Types of cells with specific functions
• Osteoporosis will be the most abundant
• Matrix is important
• For bones they will need the osteocyte to make sure there is contact with the nerves and vessels throughout the bone.
• Osteoclasts do bone remodelling that is important or shaping/structuring

Basic Functionality

• The remodeling happens via two cells bone building and bone destruction
• Then the creation of bones
• The arrangement of the cellular matrix determines their structure
• Osteon's are the primary bone cell groups
• This system allows for strength of bones.

Blood and Innervation

• The blood vessels have a set path.
• The vessels of the bone do not transverse the bone structure that we call "Bone Material

Description of the "microstructure"

• Is formed by both lamellae a material
• Osteonic
• Interstitial
• Inner or outer * Inner
• Canaliculi that surround the blood vessels.

Two Types of Bones

• Compact bone
• Spongy bone
• The compact and spongy regions are classified by their density

Bone Creation

• Starts with a bone remodeling cell that develops.
• This creates the bone

Intermembraneous Ossification

• That bone creation with messenchyme
• Bones will contain matrix for bones to attach
• This converts the bone into bone material

Endochondral Ossification

• Cartilage is replaced

What Cartilage Does

• Nutrients flow throughout
• Stoping nutrients will stop cells.
• This means they stop the matrix as well,
• This creates structure
• These processes creates a structure for bones

Structure

• The development creates structure throughout bones

Epiphyseal Region

• Consists of cartilage

How Is Bone Produced

• Bone creation works in five steps. So it keeps the current width of the skeleton while maintaining the original length.

How Is Cartilage Produced.

• Cartilage functions as replacement in skeletal joints

What Happens to Cells Damaged

• Damaged cells will be met by a wave of new cellular growth.
• Wave travels down ECM to rebuild new materials.

Tissue Replacement

• The tissue will not be entirely replaced due to the inability to conduct that process.
• As cells die, tissue will be filled in.
• Collagen will not allow proper cell growth

Muscle Tissue

• Classified by its unique ability to contract
• Arises from a mesodermal origin
• Contains cells and tissues specialized for movement

Functions

• Body posture
• Digestion
• Bloodflow
• Heat creation

Smooth Muscle cell

• Are for blood vessels or digestive systems Smooth have lower speeds of contraction

Skeletal

• For the movement of limbs and are the fastest and highest intensity

Cardiac

• For the movement of the heart in smooth rhythmic motion

Muscle Tissue Composition

Skeletal Muscle:

• Consists of multiple cylindrical sections.
  • Allows for attachment to surrounding cells
  • Features lines
    • Contracts rapidly

The Cellular Region

• Is organized along shorter segments than skeletal muscle
• Has high amount connection

Important Characteristics

• Includes striated lines
• Relies on rhythmic motion to stimulate contraction

Smooth Muscle Composition

• Spindle shaped
• Long chain
• Has 1 singular nucleus
• Lacks attachment to other surrounding regions

Description

• Contains all 3 muscles.
• Is able to modify contractions based on Autonomic
• Nervous structure through Sympathetic and Parasympathetic nerves

Important Details About Muscle

• Smooth Have no control over their functions Therefore. In most cases they operate functions on their own
• The tissue origin is what dictates their function

Muscle Development

• Begin as myoblasts, which is the origin of muscle production

What Myoblasts Do

• Unite structure to make tube in which structural proteins form together
• The proteins turn into the actual muscle fibers

Regeneration

• Occurs with smooth muscle or cardiac muscle that have the ability to regenerate depending on where the tissue is and how its structured

What is The Main Focus to Assist Regeneration

• Stem cell
• In assisting the body’s regenerative power

How The Fibers Form

• Fibers that form together to create structural functions.

How Cells Become Attached

• Cells form together with membrane proteins in which create the structural support

Internal Features inside cellular Matrix

• Inside cellular matrix the structure will be comprised from proteins that allow expansion or contraction

Function

• Actinin stabilizes

Myosin Stabilized

• It by the m-band and the protein that are part of this
• H is a region that is only a thick and that is another distinct section
• In the middle of h there is an axis

Thin Filaments

• It is in this zone that is connected by connections to structure support

Muscle Cells Are Made of Repeating Parts Called sarcomeres

• Each sarcomere has different zone

Each zone differs dependent on the type and function