Epithelial and Connective Tissues

• Tissues consist of cells that are similar in structure and work together to perform a common function
• The four types of tissue are: connective, epithelial, muscle, and nervous

Epithelial tissue

• Covers exposed surfaces such as skin
• Lines internal passageways
• Forms glands

Epithelial Tissues: Functions & Structure

• Cover surfaces and provide protection like skin and cavity linings
• Cell junctions are tightly packed to make a barrier
• Cells have an apical surface, which is always on top, and a basal surface; these surfaces differ in structure and function
• Goblet cells are unicellular glands that perform secretion
• Cilia moves substances along the surface of the cell
• Microvilli increases surface area for absorption and secretion
• Keratinized cells are dead cells filled with keratin protein which helps against abrasion, such as skin
• The basal surface has a basement membrane
  • Made up of collagen and glycoprotein, the basement membrane attaches the epithelium to connective tissue underneath
  • It provides room for cell mitosis
  • It determines what enters the epithelium from connective tissue below
• Epithelial tissue is avascular meaning it has no blood vessels; it gets blood from connective tissue below the basement membrane
• Epithelial tissue regneration is fast
• It has a lot of nerve endings

Classification of Epithelia

• Epithelia are classified by their shape and the number of layers of cells

Cell Shapes

• Squamous epithelia are thin and flat
• Cuboidal epithelia are square shaped
• Columnar epithelia are tall, slender rectangles

Cell Layers

• Simple epithelium has a single layer of cells
• Stratified epithelium has several layers of cells and is named according to the cells at its free surface

Squamous Epithelia

• Simple squamous epithelium performs absorption, diffusion, and reduces friction as found in the lung and kidney tubules
• Mesothelium lines body cavities
• Endothelium lines the heart, blood, and lymphatic vessels

Simple Squamous

• Single layer of flattened cells with disc-shaped central nuclei and sparse cytoplasm
• Allows for passage of materials by diffusion and filtration where protection is not important; it also secretes lubricating substances in serosae
• Simple Squamous Location: Kidney glomeruli, air sacs of the lungs, lining of the heart, blood vessels, and lymphatic vessels as well as lining of the ventral body cavity (serosae)

Simple Cuboidal

• Simple Cuboidal tissue performs secretion and absorption
• Glands, ducts, kidney tubules
• Limited Function: protection, secretion, absorption

Simple Columnar

• Simple Columnar tissue performs absorption and secretion
• It lines the stomach, intestine, and uterine tubes
• Protection, secretion, absorption

Stratified Squamous

• Protects against attacks and abrasions; such as skin and inside the mouth
• Keratin protein adds strength and water resistance as found in skin tissue

Stratified Cuboidal Epithelia

• Found in sweat ducts and mammary ducts

Transitional Epithelium

• Tolerates repeated stretching and recoiling cycles without damage and appearance changes as stretching occurs
• Locations: Urinary bladder, renal pelvis, and ureters
• Function: Permits expansion and recoil after stretching

Pseudostratified Columnar

• Appears like it is stratified
• Each cell attaches to the basement membrane
• Not all cells make it to the free surface
• Located in respiratory tract

Glandular Epithelia

• Endocrine glands release hormones into interstitial fluid and have no ducts
• Exocrine glands produce secretions onto epithelial surfaces and transport through ducts

Classification of Epithelia: Glandular Secretion Type

• Merocrine secretion occurs as vesicles release secretions via exocytosis
  • Examples include sweat glands, salivary glands and the pancreas
• Apocrine secretion happens as secretions are released via shedding of the cytoplasm as found in the mammary gland
• Holocrine secretion occurs as gland cells are replaced by stem cells while cells burst, killing gland cells, as seen in the sebaceous gland

Connective Tissues

Types of Connective Tissue

• Fibrous Connective Tissue (forming a tendon)
• Adipose Tissue
• Cartilage
• Loose Connective Tissue (under your Skin)
• Bone
• Blood

Function of Connective Tissues

• Connect epithelium to the rest of the body through the basal lamina
• Provide structure and support by bone
• Store energy through fat Transport materials using blood
• Has no contact with environment

Characteristics of Connective Tissue

• Connective tissues have scattered cells
• The Matrix is made up of Ground substance & Fibers
  • Collagen fibers are strong and flexible
  • Elastic fibers stretch
  • Reticular fibers form a network of fine collagen fibers

Matrix Characteristic Elements

• Ground substance determines the characteristics of connective tissue
  • Blood has ground substance like water
  • Areolar, which is always below epithelium, has hyaluronic acid, a ground substance that makes it viscous, like joint fluid _ Cartilage has a ground substance of chondroitin & glucosamine
  • Bone, ground substance has calcium salt that makes it hard

Characteristics of Connective Tissues

• Vascular except for cartilage
• Has nerve ending

Types of Connective Tissue

• Connective tissue proper connects and protects
• Fluid connective tissues transport
• Supportive connective tissues provide structural strength

Cells Found Within Connective Tissues

• Fibroblasts - connective tissue proper
• Chondroblasts - cartilage
• Osteoblasts - bone
• Hematopoietic stem cells produce white blood cells, plasma cells, macrophages, and mast cells
• Plasma cells develop from B lymphocytes (B cells), fight bacteria, and stop infection and disease

Function Of Lymphocytes

• Antibody production: B cells produce antibodies that attack bacteria, viruses, and toxins
• Cell-mediated killing: T cells destroy virus-infected and cancerous cells
• Mediate response regulation: T cells help control immune responses

Connective Tissue Proper Cells

• Fibroblasts: most abundant type of cell in connective tissues proper
• Fibrocytes: the second most abundant cell type; maintains the fibers of connective tissue proper
• Macrophages: large immune system cells that eat pathogens and damaged cells
• Adipocytes: Fat cells Mesenchymal cells respond to to injury or infection, differentiating into fibroblasts, macrophages, etc
• Melanocytes synthesize and store melanin, the brown pigment
• Mast cells stimulate inflamation after injury or infection, releasing histamine and heparin

Connective Tissue Fibers

• Collagen fibers fibers are the most common, strong, flexible, and capable of resisting force in one direction like tendons and ligaments
• Reticular fibers form a network of interwoven fine collagen fibers that resist forces in many directions and form sheaths around organs
• Elastic fibers contains elastin and return to original length after stretching like elastic ligaments of vertebrae

- Embryonic Connective Tissues

• Are not found in adult
• Mesenchyme (embryonic stem cells)
  • The first connective tissue in embryos
• Mucous connective tissue
• Loose embryonic connective tissue

Loose Connective Tissues

• It contains three types in adults such as, Areolar, Adipose, and Reticular

Areolar

• Connective tissue composed of a viscous ground substance that includes hyaluronic acid
• Is the most found under epithelial tissue, is composed of Collagen, elastic, and reticular fibers
• Has Scattered cells of fibroblast and mast cells

Adipose tissue

• Connective Ground substance (hyaluronic acid)
• Prevents heat loss
• Found around organs and under skin
  • White fat (adults, one droplet of fat per cell)
  • Brown fat (newborn, several fat droplets per cell)

Reticular tissue

• Provides support via Supportive fibers (stroma) and supporting functional cells (parenchyma) such as in the spleen, liver, lymph nodes, and bone marrow

Dense Connective Tissues

• Dense regular connective tissue
• Dense irregular connective tissue
• Elastic tissue

Dense Regular

• Tightly packed, parallel collagen fibers with fibroblast cells
• Tendons attach muscles to bones, Ligaments connect bone to bone, aponeuroses attach in sheets to large, flat muscles
• It withstands great tnesile stress whens pulling forice is applied in one direction

Dense Irregular

• Connective tissue composed of interwoven collagen fibers with fibroblast cells, layered in skin, around cartilages, around bones
• Offers protection due to is strength of resistance to forces exerted from many angles

Elastic Tissue

• Made of Elastic Fibers, such as Elastic arteries of the Aorta
• Locations: True vocal cords, Elastic ligaments of Spinal Vertebrae (provides Cushion shocks)

Supportive Connective Tissues: Cartilage

• Gel-type ground substance
• For shock absorption and protection Does not contains: blood vessels or nerve ending

Bone

• Calcified from Calcium Salts providing For weight support

Cartilage

• Connective tissue containing a cartilage matrix, Chondroitin sulfates
• scattered cells, and Chrondrocytes in lacunae Perichondrium: 2Layer, dense irregular covers cartilage.

Hyaline cartilage

• Common type of cartilage that's capable of stiff yet flexible support to reduce friction between bones.
• Its components can be found in the embryonic skeleton, Synovial Joints Rib tips, and, nose trachea

Fibrous cartilage, aka fibrocartilage

• Limits Movements and resists compression while preventing bone on bone contact
• location: Knee Joints (menisci of knee) betwenn public bones interbertebal discs

Elastic Cartilage

• Supportive bends easy
• Location: external ear and Epiglottis

Supportive Connective Tissues: Osseous Tissue (Bone)

• String with (Calcified Calcium Salt Deposit)
• Contains Bone cells or osteocytes.

Features of Bone

• A membrane known as the Periosteum is the outer layer of bones with the membrane
• Consisting of both Fibourous Layer and cellular Layer

Fluid Connective Tissues

• Blood is a watery matrix with dissolved proteins but containing on fibers unless their are blood clots
• Red blood cells (erythrocytes) Transport Oxygen
• White blood cells (leukocytes) Immune System
• Platelets- clotting

Types of White blood cells and their Function

• Monocytes. They have a longer lifespan than many white blood cells and help to break down bacteria.
• Lymphocytes. They create antibodies to fight against bacteria, viruses, and other potentially harmful invaders.
• Neutrophils. They kill and digest bacteria and fungi. They are the most numerous type of white blood cell and your first line of defense when infection strikes. -Basophils. They secrete chemicals, such as histamine, a marker of allergic disease, that help control the body's immune response.
• Eosinophils. They attack and kill parasites and cancer cells and help with allergic responses.

Connective Tissue: Lymph is

• In lymph vessels
• Immunity providing a water matrix with No fibers, only White blood cells

Muscle Tissue

• Three types of muscle tissue: skeletal, cardiac, and smooth

Muscle Tissue

Skeletal:

• Striated and voluntary
• Long and cylindrical
• Is multinucleated and does not regenerate well

Cardiac:

• Striated and involuntary
• Single nucleus and form branching networks connected at intercalated discs
• Does not regenerate

Smooth:

• Non-striated and involuntary
• Single nucleus as the cells are small and tapered
• Regenerates well

Neural Tissue

• Specialized for conducting electrical impulses and concentrated in the central nervous system such as the the Brain And Spinal Cord

Composition of Neural Tissue

• There are two components: Neurons for Perform Electrical communication
• There are also Neuroglia that are supporting Cells which Provide Repair (By mitosis) supply Nutritrience

Mitosis definition

• Nuclear division that results in chrome replication through the following stages
• Become equally distributed into two daughter cells; Spindle formation

Amitosis: The Simple Cell method

• A direct cell division where there's no Spindle Fiber Format or chromosomes

Membranes

• Physical barriers to the outside environment consisting of epithelial tissue supported by aerolar connective tissue

4 Types of the membranes

• Mucous membrane ( line Passageways that have connections
• Serous Lines Cavities (not open to the outside)

4 Types pt.2

• Cutaneous, (Skin) -Synovial Membranes (line moving articulating lines )

4 Types pt.3, Features of Mucous Membranes

• Goblet Cells Epithelial surfaces are Most Laminar propria (areola tissue type)

4 types pt. 4

• Serous ( simple squamous epithilial and areola connectives)
• Line Cavity's (not Open to the outside) Reduce friction by way if peritai and viscerial serosas

Three serous membrane

• Pluera: Lines Plueral cavitys and covers the linings with peritoneum
• lines peritonial cavity and covers the abdonminal organs + the Pericardium that lines cord

Synovial Membranes

• Mostly Areololar top Tissues with few cells
• that lines articulates and provides synovial fluids to protect bones

Connective tissue: Cutaneous Membrane

• Keratinized- consists of Stratifies Squamous Epithelium
• It is a dry membrane

Tissue Repair: Inflammatory Response

• Bleeding is reduced as histamine is released from mast cells (dilation)
• It increases blood flow with more plasma anti-bacterial bodies and agents
• Signs include swelling, redness and swelling

Tissue Repair: Granulation Proliferation

• Phase Building and connective tissues are composed of new layers and new blood vessels
• With new collagen fibers

Tissues/scar

tissue - Maturation (Scaving / Regenration)

• There are damaged
• The same cell is been changed , restored with cut surface

Tissues: Scar Tissue

• Damaged tissue replaced with collagen
• (fibrousis). No normal function
• Parenchyma lead regenerate to the stromal cells to cause Fibrous

Explore exocrine and endocrine glands, holocrine secretion, and connective tissue components. Discover the roles of connective tissues and properties of epithelial tissues. Learn about apical surface specializations and the function of the basement membrane.