Exam 2 BIO214

What are the four broad categories of tissues?

\-Epithelial Tissue

\-Connective Tissue

\-Nervous Tissue

\-Muscular Tissue

Organ

a structure with discrete boundaries that is composed of two or more tissue types

Histology (microscopic anatomy)

the study of tissues and how they are arranged into organs

Tissue

a group of similar cells and cell products working together to perform a specific role in an organ

What do the four primary tissue types differ in?

\-types and functions of their cells

\-characteristics of the matrix (extracellular material)

\-relative amount of space occupied by cells versus matrix

Matrix

extracellular material

What is the matrix composed of?

\-fibrous proteins

\-ground substance

-also known as tissue fluid, ECF, interstitial fluid, or tissue gel

Ground Substance

a component of the matrix, clear gel

Embryonic Tissues

\-a fertilized egg becomes an embryo with layers

\-Ectoderm, Endoderm, Mesoderm

Ectoderm

\-outer

\-gives rise to epidermis and nervous system

Endoderm

\-inner

\-gives rise to mucous membrane lining digestive and respiratory tracts, digestive glands, among other things

Mesoderm

\-middle

\-becomes gelatinous tissue called mesenchyme

\-wispy collagen fibers and fibroblasts in gel matrix

\-gives rise to cartilage, bone, blood, muscle

What do histologists do?

preserve, slice, and section tissues

How many cells thick is the desired microscope slide?

1-2

Stains

tissue is mounted on slides and artificially colored with histological stain

-stains bind to different cellular components

Charactertists of slices

\-some slices miss the cell nucleus

\-in some slices, the cell and nucleus appear smaller

Longitudinal Section

tissue cut on its long axis

Cross Section or Transverse Section

tissue cut perpendicular to long axis of organ

Oblique Section

tissue cut at an angle between cross and longitudinal sections

Smear

tissue is rubbed across a slide

-e.g., blood

Spread

some membranes and cobwebby tissues are laid out on a slide

-e.g., areolar tissue

Epithelia are sheets of ____ adhering cells, one or more cells thick

closely

Epithelial tissue constitutes most ____

glands

Avascular

\-does not have blood vessels

\-usually nourished by underlying connective tissue

Functions of Epithelial Tissue

\-protect deeper tissues from injury and infection

\-produce and release chemical secretions

\-excrete wastes

\-absorb chemicals including nutrients

\-selectively filter substances

\-sense stimuli

Characteristics of Epithelial Tissue

\-some epithelial cells are very close together

\-have a high rate of mitosis

\-have a basement membrane

\-have a basal surface

\-have an apical surface

Basement Membrane

\-layer between an epithelium and underlying connective tissue

-collagen, reticular proteins, glycoproteins, other protein-carbohydrate complexes

-anchors the epithelium to the connective tissues below

Basal Surface

surface of epithelial cell facing the basement membrane

Apical Surface

surface of epithelial cell that faces away from the basement membrane

Simple Epithelia characteristics

\-contain one layer of cells

\-named by shape of cells

\-all cells touch basement membrane

Stratified Epithelia characteristics

\-contain more than one layer

\-named by shape of apical cells

\-some cells rest on top of others and do not touch basement membrane

What are the four types of Simple Epithelia?

\-simple squamous

\-simple cuboidal

\-simple columnar

\-pseudostratified columnar

Pseudostratified Columnar

\-falsely appears stratified, as some cells taller than others

\-every cell reaches the basement membrane (but not all cells reach the free surface)

Goblet Cells

wineglass-shaped mucus-secreting cells in simple columnar and pseudostratified epithelia

Simple Squamous Epithelium

\-single row of thin cells

\-permits rapid diffusion or transport of substances

\-secrets serous fluid

\-locations: alveoli, glomeruli, endothelium, and serosa

Simple Cuboidal Epithelium

\-single layer of square or round cells

\-absorption and secretion, mucus production and movement

\-locations: liver, thyroid, mammary and salivary glands, bronchioles, and kidney tubules

Simple Columnar Epithelium

\-single row of tall, narrow cells

\-oval nuclei in basal half of cell

\-brush border of microvilli, ciliated in some organs, may possess goblet cells

\-absorption and secretion; secretion of mucus

\-locations: lining of GI tract, uterus, kidney, and uterine tubes

Pseudostratified Epithelium

\-looks multilayered, but all cells touch basement membrane

\-nuclei at several layers

\-has cilia and goblet cells

\-secretes and propels mucus

\-locations: respiratory tract and portions of the male urethra

What are the three types of Stratified Epithelia named after their shapes?

\-Stratified Squamous

\-Stratified Cuboidal

\-Stratified Columnar (rare)

What is the fourth type of Stratified Epithelia?

Transitional Epithelium

What is the most widespread stratified epithelium of the body?

Stratified Squamous

What do the deepest layers of Stratified Epithelia undergo?

\-continuous mitosis

\-daughter cells push toward the surface and become flatter as they migrate upward

\-finally die and flake off- exfoliation or desquamation

What are the two kinds of Stratified Squamous Epithelia?

Keratinized and Nonkeratinized

Keratinized Stratified Squamous Epithelium

\-found on skin surface, abrasion resistant

\-multiple cell layers; cells become flat and scaly toward surface

\-resists abrasion; retards water loss through skin; resists penetration by pathogenic organisms

\-locations: epidermis, palms and soles heavily keratinized

Nonkeratinized Stratified Squamous Epithelium

\-lacks surface layer of dead cells

\-same as keratinized epithelium without surface layer of dead cells

\-resists abrasion and penetration of pathogens

\-locations: tongue, oral mucosa, esophagus, and vagina

Stratified Cuboidal Epithelium

\-two or more cell layers; surface cells square or round

\-secretes sweat; produces sperm, produces ovarian hormones

\-locations: sweat gland ducts, ovarian follicles and seminiferous tubules

Transitional Epithelium

\-multilayered epithelium with surface cells that change from round to flat when stretched

\-allows for filling of urinary tract

\-locations: ureter and bladder

Cell Junctions

connections between two cells

Most cells are either anchored to each other or ___

their matrix

What do cells/cell junctions do?

\-communicate with each other

\-resist mechanical stress

\-control what moves through the gaps between them

Tight Junction

linkage between two adjacent cells by transmembrane cell-adhesion proteins

What do tight junctions do in epithelia?

they form a zone that completely encircles each cell near its apical pole

What do tight junctions seal off?

intracellular space, making it difficult for substance to pass between cells

Desmosome

patch that holds cells together (like a clothing snap)

What do Desmosomes do?

keep cells from pulling apart and resist mechanical stress

What arises from the cytoskeleton with Desmosomes?

hook-like, J-shaped proteins

What do the hook-like, J-shaped proteins do?

\-anchor cytoskeleton to membrane plaque

\-transmembrane proteins from each cell joined by cell adhesion proteins

Hemidesmosomes

half desmosomes that anchor basal cells of an epithelium to underlying basement membrane

Gap (communicating) Junction

formed by ring-like connexons

What do the connexons consist of?

six transmembrane proteins arranged like segments of an orange around water-filled pore

What passes between the cells of gap junctions?

ions, nutrients, and other small solutes

Where are the gap junctions located?

\-cardiac and smooth muscle

\-embryonic tissue

\-lens and cornea

Gland

a cell or organ that secretes substances for use elsewhere in the body or releases them for elimination from the body

What are glands normally composed of?

epithelial tissue in a connective tissue framework and capsule

Secretion

product useful to the body e.g., saliva

Excretion

waste product e.g., urine

Endocrine Glands

have no ducts; secrete hormones directly into blood

e.g., thyroid, adrenal, and pituitary glands

Hormones

chemical messengers that stimulate cells elsewhere in the body

Are there some organs that have both endocrine and exocrine functions?

yes

e.g., liver, gonads, pancreas

Exocrine Glands

maintain their contact with surface of epithelium by way of a duct

Examples for external and internal surfaces of exocrine glands

external: sweat and tear glands

internal: pancreas and salivary glands

Unicellular Glands

found in an epithelium that is predominantly nonsecretory

Can Unicellular glands be exocrine or endocrine?

yes

e.g., mucus-secreting goblet cells in trachea or endocrine cells of stomach

Capsule

connective tissue covering of exocrine gland

e.g., pericardial sac of the heart

Septa or Trabeculae

extensions of capsule that divide interior of gland into compartments (lobes and lobules)

Stroma

connective tissue framework of the gland

What does the Stroma do?

supports and organizes glandular tissue

Parenchyma

cells that perform the tasks of synthesis and secretion, and are typically cuboidal or simple columnar epithelium

Duct shape glands

simple (unbranched) vs. compound (branched)

Gland shapes

\-tubular

\-acinar

\-tubuloacinar

Tubular gland shape

narrow secretory portion

Acinar gland shape

secretory cells form dilated sac (acinus or alveolus)

Tubuloacinar gland shape

both tubular and acinar portions

What are the three different types of secretions?

\-Serous glands

\-Mucous glands

\-Mixed glands

Serous glands

\-watery

\-produce thin, watery secretions

e.g., perspiration, milk, tears, digestive juices

Mucous glands

\-goopy

\-produce glycoprotein, mucin, which absorbs water to form mucus

\-Goblet cells: unicellular mucous glands

Mixed glands

contain both serous and mucous cell types and produce a mixture of the two types of secretions

Apocrine secretion

\-budding

\-lipid droplet covered by membrane and cytoplasm buds from cell surface

What type of secretion is milk fat secretion from mammary glands?

Apocrine

Merocrine secretion

used by eccrine glands, uses vesicles that release their secretion by exocytosis

e.g., tear glands, pancreas, gastric glands, and others

Holocrine secretion

\-cells accumulate a product until they disintegrate

\-secretion itself is an entire cell

e.g., oil glands of scalp and skin, and glands of eyelids

What is in the mixture of Holocrine secretion?

cell fragments and synthesized substances

What are the three types of membranes?

\-Cutaneous membrane

\-Mucous membrane (mucosa)

\-Serous membrane (serosa)

Cutaneous membrane

\-the skin

\-the largest membrane of the body

What is Cutaneous membrane made of?

stratified squamous epithelium (epidermis) resting on a layer of connective tissue (dermis)

Mucous membrane (mucosa)

lines passages that open to the external environment

e.g., digestive tract

What are the sublayers to the mucous membrane?

epithelium, lamina propria (areolar tissue), muscularis mucosa (smooth muscle)

Functions of mucous membrane

absorptive, secretory, and protective functions

Do mucous membranes have mucous producing goblet cells?

yes, often

Serous membrane (serosa)

\-internal membrane