Chapter 3 - Histology: the study of tissues

Histology

study of tissues

Importance: many organic dysfunctions are diagnosed at the tissue level

specialized cells

cells uniquely suited to perform a particular function

Tissue

a group of structurally and functionally related cells and their external environment performing together common functions

pathology

study of abnormal tissues

Interpreting Tissue Sections - Tissue Preparation

fixation, section, stain, observation

Cross-section of a tissue

Longitudinal section of a tissue

Types of tissues

Epithelial

Connective

Nervous

Muscular

Epithelial tissue

Protects organs by covering/lining

Always sitting on a connective tissue. Basement membrane between the two

Connective tissue

A body tissue that provides support for the body and connects all of its parts

Muscular Tissue and Types

Contracts and moves the various parts of the body.

Three types: skeletal, cardiac, smooth

Nervous tissue

sends electrical signals through the body

Control mechanism: to control human function along with endocrine system

Tissue Makeup

Cells and Matrix

Tissue Matrix

Matrix = Extracellular material around cells that give strength and tensile and compressive forces, directs and holds cells in place, regulation of development, mitotic activity and survival

- Matrix is ground substance and protein fibers

Matrix - Ground substance

diverse consistency

contains interstitial or extracellular fluid

water

ions

nutrients

macromolecules

- glycoproteins (CAMs - cellular adhesion molecules)

- glycosaminoglycans GAGs ("trap" water in the ECM")

- proteoglycans (make ECM firmer, resistance to compression, intercellular cement)

Matrix - fibrous proteins

collagen, elastic, reticular

Nervous Tissue

composed of two types of cells:

- Neurons (functional unit of cell)

- Neuroglia - around cell

Function: transmission of information and assimilation

Transmit electrical signals

Structure is highly specialized to send and receive electrical signals

Body of cell, then extensions

Located in brain, spinal cord, nerves, and ganglia

Muscle Cells

Three types, all responsible for contraction.

Skeletal:

- Striations

- Voluntary

Cardiac

- Striations

- Branched

- Intercalcated discs

- Involuntary

Smooth

- Non-striated

- Fusiform

- Involuntary

Function: contraction, facilitate movement. Movement of difference orifices

Skeletal Muscle Tissue

Striations, voluntary

Long, cylindrical

Facilitates movement of skeleton

Long, so multinucleated

You decide how and when to contract the cell

Cardiac muscle tissue

Striations, branched, intercalated discs, involuntary

Smooth muscle tissues

non-striated, fusiform, involuntary

Eyeball, skin, wall of blood vessels

Epithelial Tissue/Epithelium

Cover/lining epithelium

Glandular epithelium

Highly cellular, little matrix

Cells are packed together by tight junctions and desmosomes

Functions:

- Protection

- secretion

- immune defense

- transport into other tissues: transcellular and paracellular, aka small intestine absorption

- sensation

Form surfaces - fast regeneration (such as in stomach)

Components:

Basement membrane connects epithelial tissue to connective tissue

Apical surface face lumen

basal lamina (glycoproteins, proteoglycans, micro filaments) and reticular lamina

Basal, lateral, and apical surface

Avascular

Highly innervated

High regeneration capacity

Classification of Epithelial Tissue

Shape:

- Squamous

- Cuboidal

- Columnar

- Transitional

Number of layers:

- simple

- stratified - more than one layer of tissue

- pseudostratified - actually simple, composed of one layer but the cells have different heights. nuclei are at different heights

Types of Simple Epithelium

one layer - shape is just different

simple squamous, simple cuboidal, simple columnar, pseudostratified columnar

types of stratified epithelium

more than one layer of cells - shape is just different

stratified squamous, stratified cuboidal, stratified columnar, transitional

Need to know what it is, where it is found in the body, and function

Simple Squamous Epithelium

Single layer of flat and irregular cells

Barely any matrix between cells

Locations: alveoli, lining heart and blood vessels, surface layer o pleura, pericardium, peritoneum, and organs, glomerular capsule

Functions: covering organs, diffusion (quick passage of CO2 or O2), smooth lining of vessels etc., secretion of serous fluid, reduction of friction

Myocardium - simple squamous separate blood and myocardium

Simple squamous cross-section

Simple Cuboidal Epithelium

Small cubes or wedge shaped cells in a single layer

Round and central nucleus

Apical surface in towards lumen

Basement membrane - sticky layer that attaches the basal surface and the underlying connective tissue

Locations: glands and glandular organs, renal tubules (reabsorption and secretion), liver, gland ducts, ovaries, thyroid follicles, vagina of a child

Function: secretion of fluids, reabsorption

simple cuboidal cross-section

simple columnar epithelium

tall cells in one layer

Oval nuclei in basal part of cell

Apical surface towards lumen:

- ciliated

- "non-ciliated/smooth": if it has microvilli or not (brush border)

mucus-secreting goblet cells

location: stomach, intestines, uterine tubes, larger bronchioles, gallbladder

function:

protection

absorption

secretion

all cells have basal side on basement membrane, on underlaying connective tissue

no gaps - such as in stomach, no gaps keep HCl acid from moving through

Simple columnar epithelium cross-section

goblet cells

a column-shaped cell found in the respiratory and intestinal tracts, which secretes the main component of mucus.

in with simple columnar epithelium

pseudostratified columnar epithelium

Looks stratified, but all cells arise from basement membrane, nuclei at different heights, often ciliated

one layer. taller than wide, nuclei at different levels - all cells are attached to basal membrane

mucus-secreting goblet cells

location: lines respiratory airways, part of male urethra, epididymus

cilia towards lumen - pseudostratified columnar ciliated epithelium (PCCE)

function: secretion of mucus, trapping of dust particles, protection to lungs

stratified epithelium

many layers, cells cuboidal at base (basal) but flattened toward the apical surface by the lumen

when classifying stratified squamous, first note there are multiple layers, but then by the shape that are closer to the apical surface

Types:

- karatinized

- nonkarantinized

location: epidermis, oral cavity, part of pharynx, adult vagina, anus, esophagus

function:

- resists abrasion and friction

- prevents pathogens from entering the tissue of the organ

- retards water loss in skin

in places that have a lot of friction and trauma

keratinized stratified squamous epithelium

skin (epidermis)

top part is dead squamous cells, then the keratinized stratified epithelium on lop of connective tissue

stratified cuboidal epithelium

location: lining of ducts of sweat glands and mammary glands

function: protection, secretion

2+ layers and lumen

transitional epithelium

many layers with tear-dropped shaped cells become flattened when stretched, cells in basal layers are cuboidal

binucleated

location: urinary bladder, umbilical cord, ureter, proximal urethra, renal pelvis

function: remarkable stretching capabilities

cross section of cells

longitudinal section of cells

Need to know name, location, and function of cells

Glandular epithelium (epithelium lines or is found as glandular)

cluster of cuboidal cells

function: secretion

types: endocrine (endocrine glands), exocrine (secretory portion and duct - transporting of secretion and releasing in a surface)(muscus, tears, etc.)

Connective tissue

More matrix, less cells widely spaced

consists of cells, protein fibers (collagen fiber, elastic fibers, reticular fibers), and ground substance (liquid (blood) to a solid (bone))

diverse

all types arise from same embryonic tissue (mesenchyme)

Function: biding of organs, support and structural framework, physical protection, movement, storage, heat production, transport

Connective tissue

Proper/fibrous

- dense - dense regular, dense irregular, elastic connective tissue

- loose - areolar connective tissue, adipose tissue, reticular connective tissue

Supportive CT

- bone tissue

- cartilidge

- bone marrow

Fluid CT

- blood

- lymph

Cells of fibrous/proper CT

Resident

- fibroblasts - stallate cells, fiber producers, hyaluronan: chemical compound responsible for viscocity to ground substance

- fibrocytes: mature fibroblasts that maintan the fibers and ground substance

- adipocytes - for storage of fat

- fixed macrophages - phagocytize foreign materials - protection

- masenchymal stem cells: divide in response to injury or infection to form other cells

Wandering Cells

- Mast cells: local inflammation - heparin and histamine

- Free macrophages - derived from monocytes

- leukocytes: lymphocytes, neutrophils, and eosinophils

Cells of Fibrous CT

Protein fibers

collagen, reticular, elastic

Protein fibers - collagen

strength, keeping cell tissue together, resistance to tissue to tensile or compressive forces, thick pink masses

form matrix

collagen protein

Protein fibers - Elastic

flexibility, ability to stretch out (distensibility) and recoil (elasticity)

smaller fibers - fine lines - squiggly

elastin protein

Protein fibers - reticular

dark lines

composed of collagen protein

Proper fibrous connective tissue: Dense Regular Connective tissue

Matrix composed of highly organized thick collagen fibers in one direction

mainly fibroblasts - make the collagen bundles and ground substance. Then have fibrocytes that maintain

tendons (skeletal muscles to bone), ligaments (bone to bone), and aponeurosis

few blood vessels

function: support in the longitudinal direction

Proper Fibrous connective tissue: Dense Irregular Connective Tissue

Random arrangement of collagen fibers

Location: most of dermis, fibrous capsules of organs and joints, perichondrium and periosteum

function: resist stress, strong support in all directions

three planes of section

ground substance

Nuclei of Fibrocyte

long and squished

Nuclei of Fibrocyte

rounder

Proper Dense Connective Tissue: Elastic Connective Tissue

Fibroblasts and fibrocytes

Fibers made of collagen and elastic fibers - made up of elastin or titin protein

Location: lining of large blood vessels, vocal cords, suspensory ligament of penis, some ligaments of spinal column

Appearance: dark, squiggly lines

Allow for stretch and stretch back

Loose connective tissue

more ground substance

Less protein fibers, loosely arranged

Occupies space between and around organs

Areolar, adipose, and reticular

Loose connective tissue: Areolar

Matrix: collagen, elastin fibers, and reticular fibers

Cells: fibroblasts, fibrocytes, mast cells (histamine and heparin) and macrophages

Location: around nerves and BV, dermis , hypodermis , as sheets of tissue between muscles, forms adventitia, synovial membrane

Function: attaches epithelial tissues, diffusion, binds organs, immune function

Characterized by mast cells: induction of inflammatory response - contain granules that have local chemical compounds called histamine and heparin and stimulates redness of tissue

Heparin - prevents coagulation of blood

Histamine:

Loose Connective Tissue: Reticular Connective Tissue

Meshwork of reticular fibers, fibroblasts, fibrocytes, and leukocytes

Location: around liver, spleen, lymph nodes, thymus, bone marrow

Function: internal framework (stroma) for soft organs

LOOKS LIKE RED BLOSSOM TREES

Loose connective tissue: adipose tissue

Asipocytes store fat, nuclei, and cytoplasms in outer part. Large, pale, open cells

Brown fat vs white fat - brown fat has multiple lipid inclusions (abundance of mitochondira, extensive blood supply) found in infants and young children (around neck and back) as you become an adult, the brown fat becomes replaced with white fat, less insulation

Obesity is a disproportionate amount of adipose tissue in comparison to lean fat.. Hypotrophic obesity

Location: hypodermis, breast tissue, outside heart, kidney, eyeballs, and joints

Function: stores energy, protection, insulation

Supportive CT

Bone marrow, cartilage (hyaline, fibrocartilage, elastic), bone/osseous tissue

Supportive CT: cartilage

matrix composed of chondroitin sulfate, semisolid gel enclosing fibers and chondrocytes (mature chondroblasts, once enclosed become mature, then maintain the matrix), produced by chrondroblasts (make the matrix)

Lacuna - cavity where condrocytes are found - indentation in ground substance

Perichondrium - band of dense irregular tissue that surround two types of cartiledge - elastic and hyaline

Avascular - exception of vascular rule - has no blood vessels - gets nutrients from being in close proximity to other vascular tissue

Hyaline

Fibrocartiledge

Elastic cartiledge

Supportive CT: Cartilage: Hyaline Cartilage

Looks like pomegranate seeds

Most common, the weakest

Location: apex of nose, larynx, trachea, articular and costal cartilage

Chondrocytes appear in pairs like "eyes"

Collagenous fibers

Perichondrium

Function: reduces friction at joints, keeps airways open, model for bone growth

Supportive CT: Cartilage: Fibrocartilage/Fibrous Cartilage

Numerous collagen fibers

No perichondrium

Location: symphysis pubis, intervertebral discs, menisci of knees

Function: Protection at weight-bearing or stressed joints, shock absorption, resistance to compression

Lucuna: inside is a chondrocyte nucleus

Supportive CT: Cartilage: Elastic Cartilage

Netlike pattern of elastic fibers around chondrocytes

Perichondrium

Location: external ear, epiglottis, auditory canal

Function: flexible framework

Matrix mostly composed of elastic protein fibers (matrix, spider web looking) - there are lacunas, and inside there chondrocytes

Body Membranes

Mucous/Mucosa

Serous/Serosa

Cutaneous - skin

Synovial - found inside joints - synovial joints

Body Membranes: Mucosa

Lines digestive, urinary, respiratory, and reproductive tracts

Composed of epithlium and lamina properia - areolar CT

Body Membranes: Serosa/Serous

Composed of simple squamous epithelium (mesothelium) and areolar CT

Produces serous fluid (transudate) derived from blood plasma

Two layers: parietal and visceral

Pericardium, peritoneum, pleura

Clinical Applications: Tissues and aging

repair and maintenance grow less efficient

Alterations of structural and chemical composition

Clinical Applications: tumor/neoplasms

benign

malignant/cancer: carcinomas, sarcomas, myelomas, leukemias, lymphomas, gliomas, myosarcomas

Tissue repair

Regeneration: replacement of dead cells

epithelial tissue - replaced with themselves connective tissue - replaced with themselves smooth muscle - replaced with smooth muscle

Fibrosis - when cells are damaged or injured, cannot be replaced with new cells - instead gap of tissue gets filled with scar tissue produced by fibroblasts going through mitosis and filling with collagen

cardiac muscle, skeletal muscle, nervous tissue