Flashcards Module 8- Complex Histology

LESSON 1A: EPITHELIAL TISSUE

Hollow organs and body cavities that do not connect to the exterior of the body, which includes, blood vessels and serous membranes, are lined by endothelium (plural = endothelia), which is a type of epithelium

tissue is highly cellular, with little or no extracellular material present between cells

capable of rapidly replacing damaged and dead cells

nearly completely avascular:

-no blood vessels cross the basement membrane to enter the tissue

-nutrients must come by diffusion or absorption from underlying tissues or the surface

Epithelial cells derive from all three major embryonic layers

1.endoderm

2.mesoderm

3.ectoderm

Endoderm

Cells lining the airways and most of the digestive system originate

Mesoderm

epithelium that lines vessels in the lymphatic and cardiovascular system

Ectoderm

epithelia lining the skin, parts of the mouth and nose, and the anus develop

basal lamina

-mixture of glycoproteins and collagen

-provides an attachment site for the epithelium, separating it from underlying connective tissue.

-attaches to a reticular lamina: is secreted by the underlying connective tissue, forming a basement membrane that helps hold it all together

FUNCTION

protection from physical, chemical, and biological wear and tear

capable of secretion and release mucous and specific chemical compounds onto their apical surface

small intestine

releases digestive enzymes

respiratory tract

secrete mucous that traps incoming microorganisms and particles.

glandular epithelium contains many secretory cells

CHARACTERIZED BY

-polarized distribution of organelles

-membrane-bound proteins between their basal surface (or bottom edge) and apical surface (or top edge)

cilia, when present, are on the apical surface

Cilia

-top edge (Apical surface)

-supported by microtubules

-beat in unison

-move fluid and particles

Ciliated epithelium in the brain

lines the ventricles of the brain where it helps circulate the cerebrospinal fluid

Ciliated epithelium of your airway

forms a mucociliary escalator that sweeps particles of dust and pathogens trapped in the secreted mucous toward the throat

Nasal cilia

sweep the mucous blanket down towards your throat

both cases, the transported materials are usually swallowed, and end up in the acidic environment of your stomach

CLASSIFICATION OF EPITHELIUM TISSUE

SHAPE + NUMBER

Shapes

squamous ("squished", flattened and thin)

cuboidal ("cubed", as wide as it is tall)

columnar ("columned", taller than it is wide)

Number

-simple epithelium (where every cell rests on the basal lamina)

-stratified epithelium (multiple layers)

-pseudostratified columnar (pseudo- = "false")

.two versions of stratified squamous coverings (keratinized and non-keratinized)

.single layer of irregularly shaped cells that give the appearance of more than one layer

three distinct simple epithelia: they are all categorized together because you will see only one stack of cells atop connective tissue

Simple squamous epithelial tissue

Simple cuboidal epithelial tissue

Simple columnar epithelial tissue

Simple squamous epithelium have the appearance of thin scales

-primary function is to provide a smooth and protective surface

-lines vessels of the lymphatic and cardiovascular system, and it is made up of a single layer of squamous cells

-the thinness of the cell, is present where rapid passage of chemical compounds is observed

-alveoli of lungs where gases diffuse, segments of kidney tubules, and the lining of capillaries are also made of simple squamous epithelial tissue

-mesothelium is a simple squamous epithelium that forms the surface layer of the serous membrane that lines body cavities and internal organs

-Mesothelial cells are squamous epithelial cells that secrete a fluid that lubricates the mesothelium

Simple cuboidal epithelium: the nucleus of the box-like cells appears round and is generally located near the center of the cell

-active in the secretion and absorptions of molecules

-observed in the lining of the kidney tubules and in the ducts of glands

Simple columnar epithelium: nucleus of the tall column-like cells tends to be elongated and located in the basal end of the cells

-active in the absorption and secretion of molecules

-forms the lining of some sections of the digestive system and parts of the female reproductive tract

Ciliated columnar epithelium: composed of simple columnar epithelial cells with cilia on their apical surfaces

-found in the lining of the fallopian tubes and parts of the respiratory system, where the beating of the cilia helps remove particulate matter

microvilli on the apical side (facing the lumen where nutrients are located) increase surface area of the epithelial cells thereby allowing high absorption of substances.

in the intestines

Stratified epithelia

-Keratinized stratified squamous epithelial tissue and Non-keratinized stratified squamous epithelial tissue

-Stratified cuboidal epithelial tissue: main tissue subclass of certain glands, especially those that secrete specialized substances like sweat, mammary and salivary glands

-Stratified columnar epithelial tissue: uncommon in the human body, but there are examples localized to the male reproductive tract (specifically, vas deferens and urethra) and found in the conjunctiva (protective structure lining some parts of the external eyeball)

Keratinized stratified squamous epithelial tissue and Non-keratinized stratified squamous epithelial tissue

-protects against physical and chemical wear and tear

Stratified squamous epithelium is the most common type of stratified epithelium in the human body. The apical cells are squamous, whereas the basal layer contains either columnar or cuboidal cells

top layer may be covered with dead cells filled with keratin

Mammalian skin is an example of this dry, keratinized stratified squamous epithelium. The lining of the mouth cavity is an example of a moist, non-keratinized stratified squamous epithelium that lacks the apical layers of dead cells (meaning living cells line the space)

Pseudostratified columnar epithelial tissue: found in the respiratory tract, where some of these cells have cilia

cells appear at different levels rather than clustered near the basement membrane due to short basal cells that end before reaching the space and slender columnar cells that start at the basement membrane and continue to the surface. The arrangement gives the appearance of stratification; but in fact all the cells are in contact with the underlying connective tissue, do not reach the apical surface.

Transitional epithelium: urinary system only ureters and urinary bladder

-bladder is empty, this epithelium is convoluted and has cuboidal apical cells with convex, umbrella shaped, apical surfaces

-bladder fills with urine, this epithelium loses its convolutions and the apical cells transition from cuboidal to squamous. It appears thicker and more multi-layered when the bladder is empty, and more stretched out and less stratified when the bladder is full and distended

LESSON 8B: CONNECTIVE TISSUE

-dispersed in a matrix

-matrix plays a major role in the functioning of this tissue

FUNCTION:

-support and connect other tissues

-protection: form of fibrous capsules and bones that protect delicate organs and, of course, the skeletal system

Specialized cells in connective tissue defend the body from microorganisms that enter the body. Transport of fluid, nutrients, waste, and chemical messengers is ensured by specialized fluid connective tissues, such as blood and lymph. Adipose cells store surplus energy in the form of fat and contribute to the thermal insulation of the body.

CLASSIFICATION: according to the characteristics of their ground substance and the types of fibers found within the matrix

-loose connective tissues: fibers are lightly organized, leaving large spaces in between

-dense connective tissues: reinforced by bundles of fibers that provide tensile strength, elasticity, and protection

-cartilage connective tissues

-special connective tissues

Mesenchyme

is the stem cell connective tissue from which all connective categories and subclasses are later derived

CELL TYPES

Fibroblast: connective tissue

Polysaccharides and proteins secreted by fibroblasts combine with extra-cellular fluids to produce a viscous ground substance that, with embedded fibrous proteins, forms the extra-cellular matrix

Adipocytes

-store lipids as droplets that fill most of the cytoplasm

-adipocytes: white and brown. The brown adipocytes store lipids as many droplets, and have high metabolic activity

-white fat adipocytes store lipids as a single large drop and are metabolically less active.

-Their effectiveness at storing large amounts of fat is witnessed in obese individuals. The number and type of adipocytes depends on the tissue and location, and vary among individuals in the population

mesenchymal cell

-multipotent adult stem cel

-can differentiate into any type of connective tissue cells needed for repair and healing of damaged tissue

macrophage cell

-large cell derived from a monocyte, a type of blood cell, which enters the connective tissue matrix from the blood vessels

-immune system

-move rapidly by amoeboid movement, engulfing infectious agents and cellular debris. In contrast, fixed macrophages are permanent residents of their tissues

-release cytokines

cytoplasmic granules

-contain the chemical signals histamine and heparin

-damaged: mast cells release histamine, an inflammatory mediator, which causes vasodilation and increased blood flow at a site of injury or infection, along with itching, swelling, and redness you recognize as an allergic response. Like blood cells, mast cells are derived from hematopoietic stem cells and are part of the immune system

Fibrocytes, adipocytes, and mesenchymal cells are fixed cells, which means they remain within the connective tissue

Macrophages, mast cells, lymphocytes, plasma cells, and phagocytic cells are found in connective tissue proper but are actually part of the immune system protecting the body

CONNECTIVE TISSUE FIBERS

collagen fibers, elastic fibers, and reticular fibers

Collagen fiber

-made from fibrous protein subunits linked together to form a long and straight fiber. Collagen fibers, while flexible, have great tensile strength, resist stretching, and give ligaments and tendons their characteristic resilience and strength. These fibers hold connective tissues together, even during the movement of the body

Elastic fiber

-contains the protein elastin along with lesser amounts of other proteins and glycoproteins; called elastin fiber

-property of elastin is that after being stretched or compressed, it will return to its original shape

-prominent in elastic tissues found in skin and the elastic ligaments of the vertebral column

Reticular fiber

-formed from the same protein subunits as collagen fibers; however, these fibers remain narrow and are arrayed in a branching network

-found throughout the body, but are most abundant in the reticular tissue of soft organs, such as liver and spleen, where they anchor and provide structural support to the parenchyma (the functional cells, blood vessels, and nerves of the organ)

ground substance

made of polysaccharides, specifically hyaluronic acid, and proteins

-ombine to form a proteoglycan with a protein core and polysaccharide branches. The proteoglycan attracts and traps available moisture forming the clear, viscous, colorless matrix you now know as ground substance.

mesenchyme, the stem cell line from which all connective tissues are later derived

replacement and repair after a connective tissue injury

loose connective tissue

-Areolar connective tissue

-Adipose connective tissue

-Reticular connective tissue

-allow water, salts, and various nutrients to diffuse through to adjacent or imbedded cells and tissues

-between many organs where they act both to absorb shock and bind tissues together

Areolar connective tissue

-fills the spaces between muscle fibers, surrounds blood and lymph vessels, lines organs in the abdominal cavity, and supports most epithelia representing the connective tissue component of epithelial basement membranes

Adipose connective tissue

-fat storage cells

-A large number of capillaries allow rapid storage and mobilization of lipid molecules

-White adipose tissue is most abundant

-protecting the kidneys and cushioning the back of the eye

-Brown adipose tissue is more common in infants; found mainly in the neck and clavicular regions of the body, thermogenic, meaning that as it breaks down fats, it releases metabolic heat, rather than producing adenosine triphosphate (ATP), a key molecule used in metabolism

Reticular connective tissue

-mesh-like

-supportive framework for soft organs such as lymphatic tissue, the spleen, and the liver (Figure 8B-3).

-Reticular cells produce the reticular fibers that form the network onto which other cells attach. It derives its name from the Latin reticulus, which means "little net".

Dense connective tissue

-Dense regular connective tissue

-Dense irregular connective tissue

-Dense elastic connective tissue

contain more collagen fibers than do loose connective tissues

Dense regular connective tissue

-fibers are parallel to each other, enhancing tensile strength and resistance to stretching in the direction of the fiber orientations.

-Ligaments and tendons are made of dense regular connective tissue, but in ligaments not all fibers are parallel.

dense irregular connective tissue

-fiber directions are random

-arrangement gives the tissue greater strength in all directions and less strength in one particular direction

-dermis of the skin is an example

Dense elastic connective tissue

contains elastin fibers in addition to collagen fibers, which allows the ligament to return to its original length after stretching.

-The ligaments in the vocal folds and between the vertebrae in the vertebral column are elastic.

Cartilage connective tissue

-Hyaline cartilage

-Elastic cartilage

-Fibrocartilage

-allow the body to maintain its posture and protect internal organs

-polysaccharides called chondroitin sulfates, which bind with ground substance proteins to form proteoglycans

-avascular, thus all nutrients need to diffuse through the matrix to reach the chondrocytes

Hyaline cartilage

-most common

-surface of hyaline cartilage is smooth. Both strong and flexible, it is found in the rib cage and nose and covers bones where they meet to form moveable joints. It makes up a template of the embryonic skeleton before bone formation

-A plate of hyaline cartilage at the ends of bone allows continued growth until adulthood.

Elastic cartilage

-elastic fibers as well as collagen and proteoglycans

-rigid support as well as elasticity

-example ear

Fibrocartilage

tough because it has thick bundles of collagen fibers dispersed through its matrix. Menisci in the knee joint and the intervertebral discs are examples of fibrocartilage

Osseous tissue: Bone

-contains mostly collagen fibers embedded in a mineralized ground substance containing hydroxyapatite, a form of calcium phosphate. Both components of the matrix, organic and inorganic, contribute to the unusual properties of bone

-Osteocytes, bone cells like chondrocytes, are located within lacunae.

-highly vascularized tissue

Blood

Leukocytes, white blood cells, are responsible for defending against potentially harmful microorganisms or molecules. Platelets are cell fragments involved in blood clotting. Some white blood cells have the ability to cross the endothelial layer that lines blood vessels and enter adjacent tissues