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Comparative Vertebrate Anatomy > Tissues > Flashcards

Flashcards in Tissues Deck (33):

What are tissues composed of?

Groups of cells that are similar in structure, function and embryological origin and are bound together by extracellular material compose tissues.

Tissues are composed of cells and extracellular nonliving material that binds cells together - this can be in form of liquid, gel, semi-solid, or solid.


Four primary tissues of body

epithelial, connective, muscular and nervous


Epithelial Tissues

Cover or line body surfaces and form glands. The free surface may have motile cilia. The intercellular space is minimal. Composed of cells, little non-living extracellular material, no blood vessels, and a basal lamina or basement membrane below the epithelium (below that connective tissue contains blood vessels) (the very thin basal lamina is primarily made of collagen fibrils, proteoglycans and water).


What is a proteoglycan

has core of protein with linear repeating polysaccharide side chains known as glycosaminoglycans (e.g. chondroitin sulphate). There are a variety of very specialized junctions between the cell walls.


How are epithelial tissues classified?

According to their shape and cell arrangement.

Remember each tissue type is composed of cells, minimal extracellular material and basement membrane.
Can also classify epithelia by location or function.


Simple Squamous Epithelium

single layer of thin flattened cells. It lines alveoli of lungs; lines blood and lymphatic vessels (endothelium); lines pleural, peritoneal and pericardial cavities (mesothelium).


Stratified squamous epithelium

more than one layer of squamous cells with the deeper layers being increasingly thicker. Found where wear and tear occur. Deeper layers divide, and surface layers die and are sloughed off. It can be nonkeratinized or keratinized; in the latter case a protein keratin is deposited as the cells die, making them impermeable to water. This type of epithelium is referred to as keratinized stratified squamous epithelium. In general, stratified squamous epithelium lines the mouth, pharynx, esophagus, anus, vagina, and forms epidermis.


Simple cuboidal epithelium

single layer of cube shaped cells. Cover ovaries, line the ducts of various glands, lines kidney tubules. May have cilia.


Simple columnar epithelium

single layer of elongated cells. Line stomach, intestine, part of the respiratory track, uterus, oviduct and gall bladder. Cilia may be present on their surfaces such as in the uterus, oviducts, and paranasal sinuses.


Pseudostratified columnar epithelium

- single layer of cells that reach the basement membrane, but some don't reach the free surface. It appears as if there is more than one cell layer, but in fact there is only one. Nuclei also found at different levels. Found in ducts of some glands (e.g. parotid gland). Respiratory passage from nose to bronchioles, including/Eustachian tubes. The free surfaces often have cilia on them (e.g. trachea).


Mucous membranes or mucosa

line digestive, urinary, respiratory, and reproductive tracts - all open to exterior. Usually stratified squamous or simple columnar with their basement membrane over a layer of connective tissue, the lamina propria, and sometimes a layer of smooth muscle called the muscularis mucosae. They lubricate, are absorptive and secretory. May secrete enzymes, all secrete mucus and are moist.


Serous membranes or serosa

these line ventral body cavities, which are generally not open to outside. Composed of a thin layer of loose connective tissue and a surface layer of simple squamous epithelium, the mesothelium with its basement membrane covered by serous fluid for lubrication. Serous membranes form the visceral and parietal pleura; parietal and visceral peritoneum; parietal and visceral pericardium.


Connective Tissue

Composed of abundant extracellular material termed extracellular matrix, and cells. The extracellular matrix is composed of: 1) "ground substance" which is composed of water with hydrophilic proteoglycans bound to long molecules of hyaluronic acid10, and 2) fibers which can be made of inextensible collagen, or reticulin, or stretchy elastin.
Fibroblast and macrophages are most common cells. Fibroblasts form the extracellular components. Macrophages are mobile cells that phagocytize foreign matter, dead or dying cells, and bacteria. Blood vessels permeate most connective tissues.


What are collagenous and reticular fibers made of?

are made of the protein collagen, which is very tough and inextensible


Reticulin Fibers

thin collagen fibers


Elastic Fibers

made of the protein elastin which is very stretchy


What are the most common cells in in CT?

Fibroblast and macrophages are most common cells. Fibroblasts form the extracellular components. Macrophages are mobile cells that phagocytize foreign matter, dead or dying cells, and bacteria. Blood vessels permeate most connective tissues.


Loose (areolar) connective tissue

most widespread connective tissue; loosely arranged. Cells are mostly macrophages and fibroblasts, has mostly collagen fibers but also elastic and reticular. It has a jelly-like ground substance. It binds the skin to underlying structures, fills in spaces, and often has adipose tissue (fat) associated with it.


Dense regular connective tissue

- reduced ground substance, fewer cells, more collagen fibers. Fibroblasts compose all of the cells and are arranged in long parallel rows in the spaces between the parallel collagen fibers. The collagen fibers are so dense that the tissue is essentially inextensible, e.g. Tendons and ligaments (as well as deep fascia12 andraponeuroses).


What type of connective tidduse is shark and fish dermis?

Shark dermis and fish dermis is dense gular connective tissue. It serves as a mechanical protector and as a whole body tendon; i.e., an exoskeleton. Thicker in female sharks, presumably because the males bite and hold onto them during copulation? The fibers form helices around all fish, wrapping the body.


Dense irregular connective tissue

e.g. human dermis: essentially a dense areolar tissue, with same elements as loose connective tissue except more and thicker collagen fibers and extensive elastic networks. The fibers are more interwoven and therefore there are fewer spaces. Sturdier than loose tissue. In man the collagen fibers have some degree of alignment, hence direction of surgical incisions is important in preventing scarring.


Elastic connective tissue

- similar to dense regular connective tissue except contains more elastic fibers and fewer collagen fibers. The spaces between the elastic fibers are filled with a delicate feltwork of collagen fibrils and a few fibroblasts. It is quite strong but stretchable (e.g. ligamentum nuchae of ruminants, walls of arteries, trachea, vocal cords, etc.).


Adipose tissue

fat tissue)13 - composed of fat cells (adipocytes) in loose connective tissue. Each cell has fat droplet that forces nucleus and cytoplasm against cell wall (stores fats and serves for protection; insulates). There is minimal matrix. Found as subcutaneous fat (hypodermis), around muscles, around heart. It is not static, fat cells get smaller or enlarge depending on use.


Supportive Connective Tissues

Three types of materials are used in the endoskeleton of vertebrates, notochord, cartilage and bone.


Connective Tissues Proper

Loose (areolar) connective tissue ,Dense regular connective tissue, Dense irregular connective tissue, Elastic connective tissue , Adipose tissue



is the plesiomorphic (ancestral) structure still present in lower chordates and in the embryos of all vertebrates. Generally the notochord is replaced by the vertebral column in the adults. In the lampreys and hagfishes it is retained in the adult being composed of a vesicular connective tissue surrounded by a cylindrical sheath and external membrane. In the elasmobranchs it is alternately expanded and constricted between the vertebrae. In most tetrapods it only remains as parts of the intervertebral discs.



Extracellular matrix is elastic and solid and has collagen fibers and proteoglycans. There are no blood or lymph vessels within it. Cartilage cells called chondrocytes lie within small spaces called lacunae within the matrix. The cells can divide and lay down new matrix (both collagen and proteoglycans), so growth can occur within the already formed cartilage (interstitial) or by deposition from cartilage cells under the tough fibrous perichondrium (appositional) that wraps the cartilage. Calcium may be present but is usually associated with cell death resulting in calcified cartilage. It is very prevalent in the endoskeleton before bone replaces a great deal of it. It is strong and flexible providing cushioning, support and protection.
Perichondrium has outer fibrous layer and inner more cellular layer. Inner layer is chondrogenic. There are three cartilage types based on character of matrix and fiber types:


What are three cartilage types?

Hyaline cartilage
Elastic cartilage


What is cartilage type based on?

The character of the matrix and fiber types.


Hyaline cartilage

bluish-white, translucent, few fibers, easily cut and damaged. Found in articulating cartilages of synovial joints, costal cartilages, in nose, trachea, bronchi, larynx



contains numerous fibers in the matrix, most are collagenous. It is also stronger, more resistant to tearing, e.g. intervertebral discs, symphysis pubis.


Elastic cartilage

yellowish color, this contains a loose network of collagenous fibers and numerous elastic fibers. It is pliable and strong: e.g. external ear, epiglottis, Eustachian tubes.



Dominant skeletal material of most adult vertebrates. The matrix is solid, containing collagen in form of fibers, some other proteins, protein-polysaccharides and glycoproteins, and calcium phosphate in the form of hydroxyapatite (Ca10 (P04)6 (OH)2).
Bones near surfaces often consist of layers of compact bone (also called lamellar bone). Often deeper in bone there is spongy or cancellous bone, where bony plates called trabeculae leave numerous spaces filled with marrow. Most trabeculae lie in the direction of the greatest stress. The shaft or diaphysis of long bones is mostly lamellar bone with a central medullary cavity; the epiphyses are spongy bone overlain by lamellar bone. The outside of the bone is lined with periosteum which has an outer collagenous fibrous layer and an inner more cellular layer. The periosteum is attached to the bone by collagenous fibers called Sharpey's fibers. Lining the inner spongy bone is a thinner endosteum.
The bone cells called osteocytes lie in small spaces, the lacunae, within the bone. These spaces intercommunicate by minute channels, canaliculi. Adult teleost bone is, however, acellular. Blood vessels permeate the bone, unlike cartilage. Once trapped inside their lacuna, bone cells (osteoblasts) are called osteocytes. Commonly, amniote lamellar bone is deposited in concentric layers called Haversian lamellae. A small central canal is left carrying blood vessels and nerves, this is called a Haversian canal. The whole structure (Haversian lamellae plus Haversian canal) is called a Haversian system, or osteon. Channels run laterally between the Haversian canals moving blood through the bone; these are Volkmann's canals. At one extreme these lead to blood vessels that pierce the bone, and at the other they lead from one osteocyte to another via the canaliculi. Around the inner and outer edge are circumferential lamellae, and areas between the Haversian systems have interstitial lamellae. Spongy bone has lacunae with osteocytes, irregularly arranged lamellae, and no Haversian system.
Bone is a dynamic tissue, always being broken down and replaced. Throughout life bone is continuously being reworked, old bone reabsorbed by osteoclasts14 and new bone deposited by osteoblasts. It adjusts its strength in response to stresses placed on it. Sustained heavy loads result in lore collagen and inorganic salts being deposited, when immobilized, salts are withdrawn. As stress patterns change, the collagen fibers and bony plates (trabeculae) realign in such a way as to provide maximal strength. Bones can add minerals on one side, remove them from another and change overall shape of the bone (how remodeling occurs is unknown). Once formed, bone growth can only occur by addition of new external layers formed from the bone forming cells, osteoblasts, under the periosteum.