Tissues: Histology Flashcards
4 types of tissue
- epithelial
- connective
- muscle
- nervous
cellularity
The condition of many cells and little material between
epithelium cells are
avascular (a = without + vascular = pertaining to small vessels) and innervated (receives nerve supply) tissue
Epithelial tissue function
protection from physical injury, sun radiation, and infection; control of permeability to avoid fluid loss from underlying tissues; and secretion of needed substances by specialized clusters of epithelium known as glands.
- protection
- secretion
- absorption
epithelium covers
- body
- organ surfaces
- lines all hollow structures
glandular epithelium
- clump-like epithelial tissue
- forms glands and secretes various products
exocrine glands
secrete products into body cavities and onto surfaces by way of tubular ducts
endocrine glands
- secretions diffuse into the bloodstream for their transport throughout the body.
- The products of endocrine glands are hormones.
free, or apical, surface
side of the cells exposed to a body space
basal surface
side exposed to the connective tissue layer
basement membrane
A thin layer of protein fibers beneath the basal surface connects the epithelial sheet to the underlying connective tissue
simple epithelium
single layer of cells
stratified epithelium
multiple layered arrangement
four alternative shapes of epithelial cells
- squamous
- cuboidal
- columnar
- transitional
squamous
flat with a thin nucleus
cuboidal
cube-shaped with a round nucleus near the center of the cell
columnar
tall with an oval nucleus near the basal surface of the cell
transitional
shape-changing from round when the tissue is relaxed to flat when the tissue is stretched
mesothelium
forming part of the peritoneum
endothelium
lining the inside wall of a large artery
Simple Squamous Epithelium
- a single layer of flattened cells
- forms the inner lining of hollow spaces
- thin structure supports the rapid movement of substances across it during diffusion
- its cells may also secrete products
Simple Cuboidal Epithelium
This tissue forms the walls of small tubes that carry fluids
can be found in
- the kidney tubules
- ducts of certain glands
- covers the surface of the ovary
makes up the secreting portion of some endocrine glands. The tissue functions in secretion and absorption, and often contains cilia or microvilli to assist in these functions.
Simple Columnar Epithelium
- single layer of tall, usually cylindrical cells
- The oval nucleus is near the basal surface of each cell
- has single celled exocrine glands: goblet cells, which produce and secrete mucus.
2 types of simple columnar epithelia
non-ciliated and ciliated
Nonciliated simple columnar epithelium
- forms an inner lining of the digestive, reproductive, and urinary tracts, and the ducts of many glands
- contains microvilli at the apical surface of cells, which aid in secretion and absorption.
Ciliated simple columnar epithelium
- lines portions of the respiratory tract, the uterine tubes, the uterus, the paranasal sinuses, and the central canal of the spinal cord
- cilia propel mucus and other substances.
Stratified Squamous Epithelium
- superficial cells are squamous (flat)
- the cells in the deepest layers are columnar or cuboidal. The layers between the two transition from columnar or cuboidal to squamous.
- forms the epidermis of the skin and lines the entry portals of the body
Stratified Squamous keratinized
- the squamous layer of cells is filled with the tough protein keratin, which provides an added protective benefit (epidermis)
Stratified Squamous nonkeratinized
esophagus
Transitional Epithelium
- the cells are usually in the process of changing between a relaxed, plump state and a contracted, flattened state
- lining the urinary bladder and portions of the ureter and urethra
- stretches to accommodate a temporary increase in urine volume
- then returns back to normal
Pseudostratified columnar epithelium
- a tissue that appears to have many layers, but in fact has only one
- misleading appearance of many layers is due to the varying shape of the cells
- may be ciliated or non-ciliated
Pseudostratified columnar ciliated form
- found lining the trachea and bronchi
- its cilia beat rhythmically to move a stream of mucus upward toward the mouth and nasal cavity
- mucus-secreting goblet cells are common in this tissue
Pseudostratified columnar ciliated form
- form lacks both cilia and goblet cells
- is found lining large ducts of certain glands, the epididymis, and part of the male urethra
mesenchyme
early connective tissue
mesenchyme turns into
- loose connective tissue
- dense connective tissue
- cartilage
- bone
- blood
matrix
- made up of protein fibers and ground substance
function of all connective tissues
is to connect and support the tissues and organs of the body
Loose connective tissue
- characterized by the presence of protein fibers that are loosely arranged and in low abundance
- primary cell type is the fibroblast, which is a large cell capable of movement throughout the semifluid ground substance.
- an important passage for blood vessels, lymphatics, and nerves coursing through the body.
Fibroblasts cells
- secreting the protein fibers of the loose matrix and many of the ground substance molecules
- found in loose connective tissue
main types of loose connective tissue
- areolar tissue
- adipose tissue
- reticular tissue
areolar tissue
- found between the skin and muscles and between other organs of the body
adipose tissue
- dominant cells are adipose cells (or adipocytes), and are capable of storing a very large volume of lipid molecules
- also an efficient insulating blanket, and a cushion that protects from injury
adipose tissue found
- areolar tissue between the skin and muscles, forming the subcutaneous fat of the superficial fascia
- the kidneys
- heart
- spleen
Reticular connective tissue
- The fibers and ground substance are produced by reticular cells, which are a specialized type of fibroblast.
- forms an internal scaffolding for certain organs: lymph nodes and the spleen.
Dense connective tissue
- characterized by a high concentration of collagen fibers, allowing relatively little ground substance and few cells
- also called fibrous connective tissue
- cells are fibroblasts, which produce the collagen fibers and ground substance
3 types of dense connective tissue
- Dense regular connective tissue
- Dense irregular connective tissue
- Elastic connective tissue
Dense regular connective tissue
- a roughly parallel arrangement of collagen fibers
- forms tendons and ligaments
Dense irregular connective tissue
- has a random arrangement of fibers
- is found in the deep layer of the skin (the dermis), in the sclera of the eyes, in the fascia in and around muscles, in capsules surrounding many organs, and in the valves and pericardium of the heart.
Elastic connective tissue
- has a dense arrangement of collagen fibers, but it is dominated a large number of branching elastic fibers
- found in the walls of large arteries, where it provides a firm but elastic structure.
Cartilage
- has a gelatinous ground substance
- the ground substance and fibers are produced by active cells known as chondroblasts, which become isolated in spaces known as lacunae (lacunae) to eventually transform into mature chondrocytes
- center of the cartilage is avascular
- prominent tissue in joints throughout the body
perichondrium
- region of protein fibers and blood vessels in cartilage
- serves as the source of nourishing interstitial fluid for the embedded chondrocytes
3 types of cartilage
- hyaline cartilage
- fibrocartilage
- elastic cartilage
Hyaline cartilage
- material at the ends of bones
- serves as a smooth surface to support bone movement at many of the body’s joints
- found in trachea & forms the rings that keep the trachea open
- ground substance of hyaline cartilage is filled with large protein-sugar molecules called chondroitin sulfate, which masks the collagen fibers weaving through it
Fibrocartilage
- dense, slightly flexible cartilage that contains bundles of collagen fibers in the extracellular matrix
- ground substance contains less chondroitin sulfate than hyaline cartilage, allowing the collagen fibers to become visible as thin wavy lines.
- present in certain joints: symphysis pubis where the hip bones meet anteriorly and the intervertebral discs
Elastic cartilage
- characterized by the presence of elastic fibers that dominate the protein matrix
- it contains chondroitin sulfate in the ground substance and chondrocytes are located within lacunae
- is a flexible tissue that supports the framework of the ears, the end of the nose, and the lid between the pharynx and the larynx called the epiglottis.
Bone Tissue
- form of connective tissue with a hard extracellular matrix
- supports other tissues
- stores mineral salts like calcium and phosphorus
- participates in body movement by its attachment to muscles
- contains red marrow where blood cells are manufactured and released into the bloodstream
- extracellular matrix consists of inorganic salts, including calcium phosphate
lamellae in bone tissue
matrix is organized in layers
osteoblasts
Bone tissue is produced by mobile bone cells
lacunae
- osteoblasts cement themselves into lacunae, and become immobile
osteocytes
immobile, mature bone cells
How do osteocytes obtain nourishment?
- The osteocytes receive nourishing interstitial fluid by way of diffusion through tiny canals that penetrate the lamellae, known as canaliculi
- allowing the entombed cells to communicate to one another and a central canal that transmits blood vessels, called the osteonic (central) canal
Compact bone
- very dense tissue that is composed of repeating cylindrical units
- each unit is called an osteon, and consists of a central osteonic canal surrounded by lamellae with osteocytes within lacunae
Spongy bone
- consists of thin plates of bone
- the spaces between the plates are filled with red marrow, which is the site of blood cell formation.
Blood
- connective tissue
- ground substance: plasma
- cells of blood are referred to as formed elements include red blood cells, white blood cells, and fragments of cells known as platelets
Blood function
- performs the vital function of transporting oxygen and carbon dioxide to and from body cells, and waste materials, hormones, enzymes, nutrients, and other vital materials throughout the body
Muscle tissue
- consists of specialized cells containing molecular filaments of protein
- protein filaments enable the cells to shorten in length, or contract
muscle tissue functions
- body movement
- temperature regulation
3 types of muscle tissue
- Skeletal muscle tissue
- Cardiac muscle tissue
- Smooth muscle tissue
Skeletal muscle tissue
- is attached to bones, and is the primary tissue of the muscular system
- extremely long and cylindrical in shape
- is striated
cardiac muscle tissue
- forms the wall of the heart
- are branched in shape, contain striations, and contain specialized junctions between adjacent cells called intercalated discs
Smooth muscle tissue
- forms sheets that contribute to the walls of hollow organs, such as blood vessels, stomach, and small intestine
- its cells are spindle-shaped with a single nucleus, and lack striations
- Smooth muscle contraction propels substances through the hollow organs, and is involuntarily controlled by the brain.
Nervous tissue
- differs from the other types of tissues by the presence of cells that are highly specialized to communicate with other cells by electrochemical signals
- cells are called: neurons, populate the brain, spinal cord, and nerves
- neuroglia (non-conductive) support neurons
2 types of membranes
- epithelial membranes
- synovial membranes
Epithelial membranes
- composed of one or more layers of epithelial cells bound to an underlying layer of connective tissue
3 types of Epithelial membranes
- Cutaneous membrane
- Mucous membranes
- Serous membranes
Cutaneous membrane
- skin, or integument
- does not secrete a lubricating fluid
- is keratinized stratified squamous epithelium of the epidermis.
Mucous membranes
- line the openings into the body, the digestive tract, and the respiratory tract
- composed of epithelium that secretes mucus, which is a viscous, sticky fluid
- for the openings into the body, the epithelium is stratified to provide a protective function, by the help of mucus
- Beneath the epithelium is a layer of loose connective tissue, known as the lamina propria
- Mucous membranes are also known as mucosae.
Serous membranes
- line body cavities and cover the surfaces of many internal organs
- The epithelium is usually a single layer of squamous cells (simple squamous epithelium) which is associated with a small amount of areolar tissue
- The epithelial cells produce a watery lubricating fluid called serous fluid
- Serous membranes are also known as serosae.
Synovial membranes
- composed entirely of connective tissue
- They line the cavities surrounding the joints, forming a smooth surface and a lubricating fluid (synovial fluid).
