Histology and Disease

Epithelial Cells

• Avascular tissue lacks direct blood supply
• Derived from Greek words "epi" (upon) and "thele" (nipple)
• Most epithelial tissues continuously renew
• Have distinctive shapes: spherical, elongated, or epileptic
• Nutrients delivered by diffusion from blood vessels in connective tissue

Basic Functions

• Protection from abrasion and injury (e.g., skin and esophagus)
• Absorption of material from lumen (e.g., tubules in kidney, small/large intestine)
• Transportation of material along the surface (e.g., cilia-mediated transport in the trachea)
• Secretion of mucus, hormones, and proteins (e.g., glands)
• Gas exchange (e.g., alveoli in the lungs)
• Lubrication between two surfaces (e.g., mesothelium of the pleural cavity)

Classification of Epithelial Tissue (Polyhedral)

• Simple: One layer of cells
• Stratified: Two or more layers of cells
• Squamous Epithelium: Flat cells
• Cuboidal Epithelium: Cube-like cells
• Columnar Epithelium: Column-like cells
• Transitional Epithelium: Urothelium (seen in urine)

Common Types of Covering Epithelia

• Simple Squamous Epithelium: Facilitates movement of viscera (mesothelium), active transport by pinocytosis and secretion
• Cuboidal Epithelium: Covering of the ovary and thyroid. Covering, secretion
• Columnar Epithelium: Lining of the intestine and gallbladder. Protection, lubrication, absorption, secretion
• Stratified Squamous (keratinized/dry): Epidermis. Protection; prevents water loss
• Stratified Squamous (nonkeratinized/moist): Mouth, esophagus, larynx, vagina, and anal canal. Protection; prevents water loss
• Stratified Cuboidal: Sweat glands, developing ovarian follicles. Protection, secretion
• Transitional: Bladder, ureters, and renal calyces. Protection, distensibility
• Columnar: Conjunctiva. Protection
• Pseudostratified: Lining of trachea, bronchi, and nasal cavity. Protection, secretion. Cilia-mediated transport of particles trapped in mucus out of air passages

Specializations of Epithelial Cells (Apical Domain)

• Cilia: Elongated, motile structures aiding in material transport on the epithelial surface and arise from basal bodies
• Microvilli: Smaller than cilia, composed of actin microfilaments, anchored to a terminal-web structure, aiding in absorption

Specializations of Lateral Surface (Lateral Domain)

• Zonula Occludens (Tight Junction): Completely surrounds apical cell borders to seal the intercellular cleft
• Zonula Adherens (Adhering Junctions): Located beneath tight junctions, forms a bond-like junction to attach adjacent cells
• Desmosomes: Located beneath adhering junctions; assist in cell-to-cell attachment
• Gap Junction: Communicating junctions allow passage of ions and small molecules between adjacent cells

Basal Lamina

• A sheet of material that basal surfaces of all epithelial cells connect with, located next to underlying connective tissue
• Composed of laminin, type IV collagen, entactin (nidogen), and proteoglycans
• Laminin are glycoprotein molecules that self-assemble into a lace-like sheet
• Type IV Collagen are monomers that self-assemble into a sheet associated with the laminin layer
• Entactin (nidogen) is a glycoprotein and proteoglycan that links laminin and type IV collagen sheets
• Reticular Lamina: Located below the Type IV collagen layer and consists of Type III collagen made for anchoring fibrils

Simple Squamous Epithelial Cell

• One-layer of uniform flat cells resting on the basement membrane and are the simplest of epithelial cells
• Smooth apical surfaces with cell width greater than height
• Allows passage of materials, secretes lubricating substances, and is located in lining blood vessels, the posterior surface of the cornea, lymphatic vessels, and lining body cavities

Simple Squamous Epithelial Cell Clinical Significance

• Mesothelioma: A neoplasm from pleural and peritoneal cavities, linked to asbestos exposure or smoking
• Endothelial Cells: They are flattened, elongated, parallel to blood flow, and rest on a basement membrane
• The tunica intima consists of the endothelium, subendothelium connective tissue, and the internal elastic lamina.
• Endothelial cells are linked by junctionals called hemidesmosomes
• Atherosclerosis: Deposits of cholesterol, lipid material, and lipophages; hardened deposits may lead to vascular occlusion, stroke, and are affected by endothelial dysfunction

Simple Cuboidal Epithelial Cell

• Composed on one layer of uniform, cubed cells on a basement membrane
• The cells are equal in height, depth, and width, with centrally located spherical nuclei
• Functions: secretion and absorption
• Location: Distal and collecting tubules of the kidney and some excretory glands

Simple Cuboidal Epithelial Cell Clinical Significance

• Hyperthyroidism (Goiter): Characterized by excess thyroid production, with symptoms like nervousness, tremors, treatable in patients with iodine-131
• Grave's Disease (Diffuse Toxic Goiter): The most common form of hyperthyroidism, an autoimmune disease from antibodies for the TSH receptor, treatable of patients with iodine-131
• Hashimoto's Thyroiditis: Most common cause of hypothyroidism, associated with thyroid gland enlargement (goiter), characterized by TSH and TPO antibody

Simple Columnar Epithelium

• One layer of cells resting on a basement membrane and are taller in height then they are wide
• Elongated nucleus that are basally-located
• Functions in absorption, secretion of mucus, enzymes, and ciliary action
• Location: digestive tract, Fallopian tubes in the female reproductive system, and ductuli efferences testis of the reproductive system

Simple Columnar Epithelial Cell Clinical Significance

• Celiac (coeliac) Disease: Gluten allergy, disorder of the small intestine due to microvilli damage
• Intestinal lining can not absorb, causing anemia and/or bone damage.
• Histologic features include blunting of villi, presence of lymphocytes, and increased lymphocytes within the lamina propria

Pseudostratified Columnar Epithelium

• A single layer of non-uniform cells varying in shape and height, can be classified as basal cells or stem cells
• Most widespread type can be found in the respiratory tract with fingerlike motile structure cells
• Functions in secretion, population of mucus, and ciliary action
• Locations: Ciliated variety found in trachea and upper respiratory tract. Nonciliated types found in the male sperm carrying duct

Pseudostratified Columnar Epithelial Cell Clinical Significance

• Bronchitis: Acute or chronic inflammation of the bronchial tubes
• Inflammation caused by viral/bacterial infections or by irritants of the bronchi

Stratified Squamous Epithelium

• Contains multiple cell layers in which top layer is composed of flattened cells
• Protects body from injury abrasion dehydration and infection
• Found: Oral cavity, esophagus, vagina, and true vocal cords (nonkeratinized)

Stratified Squamous Epithelium Clinical Significance

• Psoriasis: A chronic inflammatory skin disease with pink or salmon plaques with silver scales with the T-lymphocyte-mediated immunologic reaction

• Barrett Syndrome: A complication of gastroesophageal reflux disease marked metaplasia of the SSE of the distal esophagus

Stratified Cuboidal Epithelium

• Upper most layer: Columnar, most basal level: cuboidal
• Made of 2-3 layers
• Location: conjuctiva, some exocrine glands
• Blockage from ducts, most common: salivary stone (calculus/calculi), removal of stone may include surgery

Transitional Epithelium

• A stratified epithelium referred to as a urothelium that line excretory channels leading from the kidney such as the renal calyces, ureters, bladder and proximal segment of the urethra
• Surface can be described as "dome shaped" and are called dome cells (they can contain two nucleoli) or umbrella cells (which contain extra membrane)

Glandular Epithelia

• Composed of epithelial cells but are classified based on of how the secretory products leaves the gland
• Endocrine Glands: release products into interstitial fluid or directly into the bloodstream
• Exocrine Glands: secrete products through ducts into the lumen or directly onto the body surfaces
• Serous gland: watery proteinaceous fluid (EX. parotid, von Ebner of the tongue, pancreas, and sweat gland)
• Mucous gland: secretes mucus, a mixture of glycoprotein and water (EX. goblet cells in the small and large intestine, respiratory epithelium, hard and soft palates, stomach epithelium)
• Seromucous (mixed) gland: have both serous and mucous secretion (EX. submandibular, sublingual, tracheal glands)
• Sebaceous gland: produce lipids (skin)

Classification of Exocrine Gland Mechanisms

• Merocrine (eccrine): only releases its secretory product w/o the loss of cell matter
• Apocrine: releases secretory product along with part of the apical cytoplasm
• Holocrine: Releases entire contents when it undergoes disintegration

Glands Classified According to Morphology

• Unicellular glands release product directly onto the the surface of a cell (ex. Goblet cells)
• Multicellular glands have secretory cells that arranges into simple and compound arrangements

Pathologic Terms

• Metastasis: Spread of malignant neoplasm from its origin site to a remote site through blood and lymphatic vessels.
• Dyslipidemia: Lipid imbalances
• Osteomalacia: Softening of bones due to defective mineralization
• Metaplasia: Where cells change shape
• Microabscess: Collection of neutrophils and debri within the parakeratotic scale of some skin in the condition psoriasis.
• Micropostule: Collection of neutrophils within the upper layer of skin
• Parakeratosis: retention of nuclei in the keratinocytes

Connective Tissue

• Mesodermal origin and contains cells, fibers, and ground substance
• Classification and function is depended on the amount of cells and composition
• Functions: provides structure for the body, metabolic support, location for lying down epithelial cells
• Vascular, unlike epithelial tissue

Types of Connective Tissue

• Connective Tissue Proper: Dense regular/irregular tissue, Loose Connective tissue
• Specialized Connective Tissue: Adipose, Reticular,Elastic tissue
• Embryonic Connective Tissue: Mesenchymal, Mucous connective tissue
• Supporting Connective Tissue: Cartilage, Bone
• Hematopoietic Connective Tissue: Blood, Bone Marrow

Cellular Differentiation of Connective Tissue

• Mesenchymal cells: Fixed cells such as adipocytes and fibroblasts
• Hematopoietic stem cells: Wandering cels such mast cells, macrophages, plasma cells, and leukocytes.
• Fibroblasts: Responsible for the the synthesis and maintenance of the extracelluar material
• Macrophages, plasma cells, and leukocytes are responsible for defense and immune function

Connective Tissue Cells

• Fibroblast: Produces fibers and ground substance, provides structural support.
• Plasma cell: Produce antibodies, assists immune system in defensive functions, and their cytoplasm appears basophilic
• Lymphocyte: Produces immunocompetent cells for immune defense and monitoring
• Eosinophilic leukocyte: Aid in inflammation.
• Neutrophilic leukocyte: Destroys foreign substances.
• Macrophage defense: Provides defense by secreting cytokines and other molecules.
• Mast cell and Basophilic: Participates in allergic reactions.
• Adipocyte: Stores nutrients like fat, energy.
• Their pale and obvious that contain well-developed RER and rich Golgi complexes.

Molecules Released from Mast Cells

• Heparin: Acts like a anticoagulant.
• Histamine: Promotes an increased vascular permeability.
• Serine protease: Activates mediators of inflammation

Plasma Cells

• Derived from B lymphocytes of the lymphatic system
• Has a lot of basophilic cytoplasm that contains a eccentrically placed nucleus.
• Can be found within the blood.
• Has "clock-face appearance" of the chromatin in the nucleus
• Has a life time of 10-20 days

Leukocytes

• Considered transient cells (appear briefly) that have the ability to move from blood vessels into connective tissue
• Cardinal indications include: Rubor signs, swelling, increased temperature and/or color.
• There are a mixture of Banded cells from different origins

Fibers

• Three types of conductive tissue fibers are the collagen fibers, reticular fibers, and elastic fibers
• Most important function is to conduct heat
• Most are made of I, II, and III
• Reticular fibers consists of the the collagen the type |||
• Type V collagen can be found in cartilage
• Elastin is important to help restore bone back to shape
• Elastic fibers are stained more darker than collagen with other stains like orcein

Ground Substances

• Ground: Highly hydrated and very transparent.
• Ground Substances, PROTEOGLYCANS, are all important

GAGs

• dermatan sulfate, chondroitin sulfates, keratan sulfate, and heparan sulfate

Dense Connective Tissue

• Made of thick collagen bundles that's packed with cylinders
• Providing high resistance in tendons and ligaments

Dense Irregular Connective Tissue

• Can be found in glands and capsules of organs
• Not greatly vascularized

Hypertrophic Scars and Keloids

• Disorder in collagen

Tendinosis

• Degenerative disease

Loose Tissue

• Provides support for organs
• Conduits used to transmit blood
• Contains a lot of mesentery

Whipple Disease

• Multisystem caused by the bacteria infection of Tropheryma whippleii

Adipose Tissue

• Two: White and Brown tissue
• Brown: Abundant for mitochondria
• Brown: hibernating bland
• White is specialized for long term storage

Brown Tissue

• Contains several small tissues together
• Called multilocular
• Contains thermogenin

Obesity

• Hypertrophic, increase in body fat
• Increases with other conditions like diabetes that could occur

Reticular Tissue

• Delicate tissue
• Provides cellular structure for tissue and organs

Elastic Connective Tissue

• Provides material
• Can be found in vertebrae
• Allow distinction and recall

Marfan Syndrome

• Effects elastic fibers
• Mutation affects those who also long limbs, hands, and feet

Mucous Connective Tissue

• Can be found in the best connective tissue.
• Can be considered Wharton's jelly

Medical Issues (U-P C-N C)

• Urticaria, skin allergic
• Pruritus, itchiness
• Cirrhosis, abnormal liver disease
• Jaundice, yellowing of the skin from bilirubin
• Coagulopathy, effects clotting
• and Necrosis

Muscle Tissue

• Cells optimize universal contractility, and drive organismal movement
• The forces needed are produced between two groups of protein
• Origin: Mesodermal
• Almost all cells differentiate
• Stains Red with H &E

Voluntart versus Involuntart

• Voluntary- Is under conscious control and also describes skeletal muscle contraction
• Invoulntary- response to autonomic control and cardiac or smooth muscle contractions

Sacroplasm

• Muscle cytoplasm
• The greek word "saroks" meaning:flash+plasma

Histological Classification

• Skeletal Muscle- Multinucleated
• Cardiac Muscle- Branched, intercalated discs, includes glycogen
• Smooth Muscle- No striations, nucleic

Skeletal Muscle

• Fibers are arranged
• Enabled the bodies muscle
• Wont work w/o neve synapses
• Striated is long multinucleated
• Muscle satellite calls remains

Development of Skeletal Muscles

• Begins a messenger fuse
• Formed from mesenchymal cells
• Myotubes synthesize protein
• Myofibalmentary light can show cross striations by reflecting protein

Organization of Skeletal Muscles

• Epimysium- an external dense sheet of muscle cells
• perimysium connective tissues layer with fascicle
• Endomysium- is a thin reticular fiber with scattered fibroblasts.
• Fiber, cappilaries in the the endomysium brings O2 and muscle fibers

3 Layers

• All 3 layer form a strong connection
• Highly organized sarcoplasm
• Formed by the Mline and the Hzone

Myofibrils

• Organized by cilindircal
• Consist of several sarcomeres

A band (dark)

• Contains filaments
• Anistrophic polarized

Ibands (light)

• Portions of thin structures
• Do not overlap

Sarcomere and sarcoplasmic

• Appears with the light microscope
• Is the contractile apparatus of the cell and extends fromz dict to district
• Mitochondria and sarcoplasm

Thick Myosin Filament

• 1.6 um long inside the abnd region

Myosin

• Complex with light or heavy light chain molecules (2)

Thick Myosin Tails

• Thin rob together an myosin

Myosin Head

• From filament cross bridges

Actin Filaments-

• Helich shaped and run filaments

Mechanism of Contraction

• Ca2 binds to troponin cells
• Filaments

FAST muscle fibers

• Specialized to contract for a short time

SLOW muscle fibers

• Contain very little glycogen

SKELETAL MUSCLES Tissues

• Muscles adopted slow contraction
• There are few capillaries if without the hormone

Smooth Muscles tissues

• Specialized for short and controlled contractions
• Influences by hormones or autonomic nerves
• Can be found with in Vessle

Smooth Muscle

• Made of small blood volume (20 um) in small areas and 50 um in pregnant woman
• Monoanucleated in central region (5_10 um)
• Lack troponin or tropomyosin with proteins

Duchenne Muscular Dystrophy

• Connective tissue by a large area w/ • Involves muscularly functioning fibroids

Cardiac Muscle

• Connected and striated but acts involuntarily
• Responsible for heart beats and contains one nucleic in cell

Hypertrophy

• Variation in muscle (cell size)
• Is the physical training of an individual
• Cell sizes increase

Myasthenia Gravis

• Autoimmune order
• Circulating antibodies
• Interferes receptors

Dystrophin

• Has a large amount of actin-binding proteins
• Involved with myofibrils
• Caused by dystrophin proteins

Ischemia

• Most injury sustained by cardiac muscle
• Heart cannot regenerate
• Can be cause by atherosclerosis

Bones

• Provides a solid support for the body
• Encloses marrow/ red blood cell
• Acts as reservoir
• Connective Tissue : Osteocytes osteoblasts and osteoclasts

Features & Functions

• Osteocytes: Found in lacuna
• Osteoblasts " growing cells
• Osteoclasts: Removes Bone Tissue

Bone Matrix

• Provides a bone harness
• Allows organization
• 50% inorganic, mainly calcium
• 50% organic mainly collagen

Bone's Protective Layers + Development

• Peristeoum & Endosteum are the layers
• Osteogenesis creates new osteoids
• They can be formed by a intramembranous ossification and the preexisiting Hyaline cartilage matrix is then eroded
• Osteoblast then secrete new osteuoids

Epiphyseal

• Consists of 5 zones that help with a Hyaline creation

Calcium

• Raises and stimulate osteoclasts for bone resorption; for bone creation
• Can be mobilize with mobilization with minerals

Joints

• The 3 joint movements include Synarthoses with limited movement, Diarthrotic are movable
• Macrophages is also contained

Medical issues of muscles & bones

• Osteoporesis, is common.
• Osteogenesis, disease; congenital.
• Osteomalacia and osteitis

Rickets

• Calcium efficiency with children's joints or muscle disorders.

Tumors

• Are uncommon
• Can develop

Naming

• Can be named with GH deficiency, for childhood reasons.

Disease

• Related for growth or bone

Cartilage

• Contains collagen elastin cells, and a tough flexible connective tissue. Is high in ECM with glycosaminoglycans
• Providing bone formulation that can be one of three types: Hayline, Elastic, & Fibrocartilage

C-E-F

• Location joints and tensile strength are the key factors
• Functions, that allows them to be smooth

ECM

• Mainly consist of type II collagen

Cell Types

• Chondrocytes: Has small amounts of cells that's high in water composition
• Cartilage contains water for a shock of absorption by making it very dense.

Perichondrium

• Contains a connective tissue that function providing nutrients, and contains progenitor cells
• Two types of growth, intersitail & Appositionial, that chondroblasts form from perichondrium

Healing

• Avascular slow, is the capacity which leads to slow cartilage movement.
• Low mitotic activity of chondrocytes. Making healing hard to do

Applications

• Osteoarthritis
• Aging, repetitive use, lead from the loss of synthesis

Hormones and Gene

• Gene affects synthesis
• Lead joint issues