AnP Lecture - Chapter 4 - Ex1

Epithelial tissue

covers body surface or lines cavities

Simple squamous epithelium Description

Single layer of flattened cells with disc-shaped central nuclei and sparse cytoplasm; the simplest of the epithelia

Simple squamous epithelium Location

Located in kidney glomeruli; air sacs of lungs; lining of heart, blood vessels, and lymphatic vessels; lining of ventral body cavity (serosae)

Simple squamous epithelium Function

Allows materials to pass by diffusion and filtration in sites where protection is not important; secretes lubricating substances in serosae - EXCHANGE, DISPOSABLE

Simple squamous epithelium

Simple cuboidal epithelium

Simple cuboidal epithelium Description

Single layer of cubelike cells

Large, spherical central nuclei

Simple cuboidal epithelium Location

Renal (kidney tubes), ovaries, thyroid

Simple cuboidal epithelium Function

Secretion and absorption

Simple columnar epithelium Description

Single layer of tall cells with round to oval nuclei;

many cells bear microvilli, some bear cilia;

layer may contain mucus-secreting unicellular glands (goblet cells)

Simple columnar epithelium Location

Non-ciliated type lines most of the digestive tract (stomach to rectum), gallbladder, and excretory ducts of some glands;

Ciliated variety lines small bronchi, uterine tubes, and uterus

Places where EXPANSION occurs

Simple columnar epithelium Function

Absorption; secretion of mucus, enzymes, and other substances; ciliated type propels mucus (or reproductive cells) by ciliary action

Simple columnar epithelium

Pseudostratified columnar epithelium Description:

Single layer of cells of differing heights, some not reaching the free surface; nuclei seen at different levels; may contain mucus-secreting cells and bear cilia.

Pseudostratified columnar epithelium Location:

Non-ciliated type in males’ sperm-carrying ducts and ducts of large glands;

Ciliated variety lines the trachea, most of the upper respiratory track, and vas deferens

Pseudostratified columnar epithelium Function

Secrete substances, particularly mucus; propulsion of mucus by ciliary action.

Pseudostratified (ciliated) columnar epithelium

Stratified squamous epithelium Description

Thick membrane composed of several cell layers; basal cells are cuboidal or columnar and metabolically active; surface cells are flattened (squamous); in the keratinized type, the surface cells are full of keratin and dead; basal cells are active in mitosis and produce the cells of the more superficial layers.

Stratified squamous epithelium Location

Nonkeratinized type forms the moist linings of the esophagus, mouth, and vagina; keratinized variety forms the epidermis of the skin, a dry membrane.

Stratified squamous epithelium Function

Protects underlying tissues in areas subjected to abrasion

Stratified squamous epithelium

Transitional epithelium Description

Resembles both stratified squamous and stratified cuboidal; basal cells cuboidal or columnar; surface cells dome shaped or squamous-like, depending on degree of organ stretch.

Transitional epithelium Location

Lines the ureters, bladder, and part of the urethra.

Transitional epithelium Function

Stretches readily, permits stored urine to distend urinary organ→ storage/increase flow.

Transitional epithelium

Stratified cuboidal Description

Cube-like and quite rare. Typically, two cell layers thick

Stratified cuboidal Location

Some sweat and mammary glands.

Stratified cuboidal Function

Secretion and absorption, 2 layers, more protection for high use but controlled functions, GLANDS, for leaking substances

Stratified cuboidal

Stratified columnar

Limited distribution in the body. Occurs at transition areas between two other types of epithelia. Apical region is columnar.

Stratified columnar Location

Pharynx, male urethra, lining some glandular ducts

Stratified columnar

No mucus movement, high impact, secretion and protection

Stratified columnar

Nervous tissue

Neurons are branching cells; cell processes that may be quite long extend from the nucleus-containing cell body; also contributing to nervous tissue are non-excitable supporting cells.

Neurons transmit electrical signals from sensory receptors and to effectors (muscles and glands); supporting cells support and protect neurons.

Located in the brain, spinal cord, and nerves.

Nervous Tissue

Skeletal muscle

Long, cylindrical, multinucleate cells; obvious striations.

Voluntary movement; locomotion; manipulation of the environment; facial expression;

In skeletal muscles attached to bones or occasionally to skin.

Skeletal muscle

Cardiac muscle

Branching, striated, generally uninucleate cells that interdigitate at specialized junctions (intercalated discs).

As it contracts, it propels blood into the circulation; involuntary control. Located in the walls of the heart.

Cardiac muscle

Smooth muscle

Spindle-shaped (elongated) cells with central nuclei; no striations; cells arranged closely to form sheets.

Propels substances or objects (foodstuffs, urine, a baby) along internal passageways; involuntary control.

Located mostly in the walls of hollow organs.

Smooth muscle

Connective tissue proper; loose areolar tissue

Gel-like matrix with all three fiber types; cells: fibroblasts, macrophages, mast cells, and some WBCs. Wraps and cushions organs; its macrophages phagocytize bacteria; plays important role in inflammation; holds and conveys tissue fluid.; edema. Supports and binds other tissue. Widely distributed under epithelia of body, e.g., forms lamina propria of mucous membranes; packages organs; surrounds capillaries.

Loose areolar connective tissue

Connective tissue proper: loose adipose tissue

Matrix as in areolar, but very sparse; closely packed adipocytes, or fat cells, have nucleus pushed to the side by large fat droplet.

Little matrix, cells are packed tight.

Provides reserve food fuel; insulates against heat loss; supports and protects organs.

Shock absorption, insulation, energy storage. Under skin in subcutaneous tissue; around kidneys and eyeballs; within abdomen; in breasts.

loose adipose tissue

Connective tissue proper: loose reticular tissue

Loose network of reticular fibers in a gel-like ground substance; reticular cells lie on the network.

Fibers form a soft internal skeleton (stroma) that other cell types including white blood cells, mast cells, and macrophages.

Lymphoid organs (lymph nodes, bone marrow, and spleen).

Loose reticular connective tissue

Connective tissue proper: dense regular

Primarily parallel collagen fibers; a few elastic fibers; major cell type is the fibroblast.

Attaches muscles to bones or to muscles; attaches bones to bones; withstands great tensile stress when pulling force is applied in one direction. Wavy.

Located in tendons, most ligaments, aponeuroses.

Dense regular connective tissue

Connective tissue proper: dense irregular tissue

Primarily irregularly arranged collagen fibers; some elastic fibers; fibroblast is the major cell type.

Collagen bundles are thicker.

Withstands tension exerted in many directions; provides structural strength.

Located in fibrous capsules of organs and of joints; dermis of the skin; submucosa of digestive tract.

Dense irregular connective tissue

Connective tissue proper: dense elastic tissue

Dense regular connective tissue containing a high proportion of elastic fibers.

Allows tissue to recoil after stretching; maintains pulsatile flow of blood through arteries; aids passive recoil of lungs following inspiration.

Walls of large arteries; within certain ligaments associated with the vertebral column; within the walls of the bronchial tubes.

Dense elastic connective tissue

Hyaline Cartilage

Amorphous but firm matrix; collagen fibers form an imperceptible network; chondroblasts produce the matrix and when mature (chondrocytes) lie in lacunae.

Most common.

Supports and reinforces; resilient cushion; resists compressive stress.

Forms most of the embryonic skeleton; covers the ends of long bones in joint cavities; forms costal cartilages of the ribs; cartilages of the nose, trachea, and larynx.

Hyaline Cartilage

Elastic Cartilage

Similar to hyaline cartilage, but more elastic fibers in matrix.

Maintains the shape of a structure while allowing great flexibility.

Supports the external ear (pinna); epiglottis.

Elastic Cartilage

Filamentous Cartilage

Matrix similar to but less firm than that in hyaline cartilage;

thick collagen fibers predominate.

Tensile strength allows it to absorb compressive shock.

Intervertebral discs; pubic symphysis; discs of knee joint.

Fibrocartilage

Bone (osseous tissue)

Hard, calcified matrix containing many collagen fibers; osteocytes lie in lacunae.

Very well vascularized.

Supports and protects (by enclosing); provides levers for the muscles to act on;

Stores calcium and other minerals and fat;

Marrow inside bones is the site for blood cell formation (hematopoiesis)

Bone (osseous tissue)

Connective tissue: blood

Red / white blood cells and platelets in a fluid matrix (plasma).

Fluid – no connection.

Transport respiratory gases, nutrients, wastes, and other substances.

Contained within blood vessels.

Blood

Tight junction vs desmosomes

Tight: no space, non-permeable, not flexible (ex: in epithelial lining to stop fluid leaking)

Desmosomes: adhere cells together but are flexible (ex: in cardiac muscles and skin to allow movement)

Epithelial Tissue: Polarity

Orientation of growth in layers of epithelial tissue (we want skin cells to grow towards the apical surface away from the basal layer/basal lamina which is the noncellular adhesive sheet made of glycoproteins and collagen)

Epithelial Tissue: Specialized Contacts

fit closely together to form continuous sheets using tight junctions and desmosomes

Reticular Lamina and Basement Membrane

Reticular lamina: deep to basal lamina, network of collagen fibers

Basement membrane: basal + reticular lamina; reinforces epithelial sheet; resists stretching and tearing, define the boundary

Epithelial Tissue: Avascular but Innervated

No blood vessels but there are nerve fibers (paper cut doesn’t bleed like crazy but still hurts)

Epithelial Tissue: Regeneration

Rapidly replaces lost cells by cell division; loss of apical-basal polarity/broken lateral contacts

Characteristics of Connective Tissue

1. Common origin: arise from mesenchyme, embryonic tissue

2. Degrees of vascularity (avascular to high)

3. Extracellular matrix (ECM)- ground substance “stuff” + fibers + cells; bear weight and endure abuse

3 Types of fibers:

1. Collagen - triple helix, strongest and most abundant, tensile strength, cross-linked fibers

2. Elastic - network long, thin elastin fibers that allow for stretch and recoil

3. Reticular - short, fine, highly branched collagenous fibers; provide more give

Components of ground substance:

1. interstitial fluid

2. cell adhesion proteins

3. proteoglycans (sugar protein) - glycosaminoglycans (GAGs) increase viscosity

Blast vs cyte

Blast- immature, actively mitotic, build up tissue (child labor)

Cyte- mature, less active, maintains tissue

Endocrine Glandular Epithelia

internally secreting hormones via exocytosis, no ducts

Exocrine Glandular Epithelia

externally secreting substances (ex: sweat), uses ducts or exocytosis to secrete directly to target organs

mucus, sweat, oil, and salivary glands

Unicellular exocrine glandular epithelium

Mucus cells and goblet cells; produce mucin (glycoprotein that dissolves in water to form mucus)

Line the intestinal and respiratory tracts

Multicellular exocrine glandular epithelium

duct + secretory unit; supportive connective tissue supplies it with blood vessels, nerve fibers, and can divide the glands into lobes

Classifying Multicellular exocrine glandular epithelium - Structure

• simple - unbranched ducts

• compound - branched ducts

Classifying Multicellular exocrine glandular epithelium - Secretory Units

• tubular - secretory cells form tubes

• alveolar: secretory units form sacs

• tubuloalveolar: secretory units form tubes and sacs

Classifying Multicellular exocrine glandular epithelium - Mode of secretion

• merocrine - most abundant, products excreted by exocytosis (pancreas, sweat, and salivary glands)

• apocrine - accumulate products within, but on the apex ruptures

• holocrine - products secreted by the rupture of gland cells (sebaceous oil glands)