Structural Organisation in Animals Test 8

 Each breast is made up of 15- 25 secretory lobes, embedded in adipose tissue. The mammary gland is like a modified sweat gland. Each of these lobes is a compound tubular acinar gland. The acini empty into ducts that are lined by cuboidal, or low columnar epithelial cells, and surrounded by myoepithelial cells.

The areolar tissue joins different tissues and forms the packing between them and helps to keep the organs in place and in normal shape.

A stratified squamous non-keratinized epithelium lines the oral surface of the lips, cheeks, floor of mouth, and covers the ventral surface of the tongue In slide 114 (human) and 114M(monkey) of the lip, note that skin (stratified, keratinized squamous epithelium with hair follicles) covers the external surface, skeletal muscle (orbicularis oris muscle) forms the core, and a mucosal epithelium(stratified, non-keratinizing squamous epithelium) covers the internal surface. 

Transitional epithelium is a stratified tissue made of multiple cell layers, where the cells constituting the tissue can change shape depending on the distention in the organ. When the organ is filled with fluid, cells on the topmost layer of this epithelium can stretch and appear flattened. Alternately, they can also appear cuboidal with a rounded shape when the fluid pressure is low.

This epithelium is found lining the urinary bladder, ureters and urethra, as well as in the ducts of the prostrate gland.

The epithelial lining of the gall bladder consists of simple columnar cells specialized for absorption, with an apical brush border of microvilli, very similar to intestinal absorptive cells.  However, unlike intestinal epithelium, gall bladder epithelium includes only this single cell type; it has no goblet cells.

Correct Answer :- a

Explanation : The palatine tonsil is composed of lymphoid tissue within which are channels lined by squamous epithelium—crypts—that open onto the surface. It is part of a ring of lymphoid tissue in the oral cavity and nasopharynx—Waldeyer’s ring—which includes also the lingual tonsil at the base of the tongue and the pharyngeal tonsil or adenoid in the nasopharynx. There are about 20 crypts reaching the deepest part of the structure. Submucosal glands lie in the peripheral part.

Endothelium refers to cells that line the interior surface of blood vessels and lymphatic vessels, forming an interface between circulating blood or lymph in the lumen and the rest of the vessel wall. It is a thin layer of simple, or single-layered, squamous cellscalled endothelial cells. Endothelial cells in direct contact with blood are called vascular endothelial cells, whereas those in direct contact with lymph are known as lymphatic endothelial cells.

Cuboidal epithelia have a cube-like shape; that is, their width is approximately equal to their height. They may exist in single layers or multiple layers depending on their location in the body.

The Bartholin's glands (also called Bartholin glands or greater vestibular glands) are two pea-sized compound racemose glands which are located slightly posterior and to the left and right of the opening of the vagina. They secrete mucus to lubricate the vagina. They are composed of cuboidal epithelium.

A stratified squamous epithelium consists of cells arranged in layers upon a basal membrane. Only one layer is in contact with the basement membrane; while the other layers are adhered to one another to maintain structural integrity. 
This type of epithelium is well suited to areas in the body subject to constant abrasion, as it is the thickest layer. Additionally, this layer can be sequentially sloughed off and replaced before the basement membrane is exposed. It forms the outermost layer of the skin and the inner lining of the mouth, esophagus and vagina. Non-keratinised surfaces must be kept moist by bodily secretions to prevent them from drying out. Examples of non-keratinized stratified squamous epithelium include cornea, lining mucosa of the oral cavity, esophagus, anal canal, vagina and the internal portion of the lips.

The corneal epithelium is the outermost layer of the cornea. It is composed of a single layer of basal cells and 4-5 cell layers of nonkeratinized, stratified squamous epithelial cells, which are held together by tight junctions, to form an effective barrier against fluid loss and pathogen penetration.

Epithelial tissues are derived from all of the embryological germ layers:

• from ectoderm (e.g., the epidermis)
• from endoderm (e.g., the lining of the gastrointestinal tract)
• from mesoderm (e.g., the inner linings of body cavities)

However, it is important to note that pathologists do not consider endothelium and mesothelium (both derived from mesoderm) to be true epithelium. This is because such tissues present very different pathology. For that reason, pathologists label cancers in endothelium and mesothelium sarcomas, whereas true epithelial cancers are called carcinomas. Additionally, the filaments that support these mesoderm-derived tissues are very distinct. Outside of the field of pathology, it is generally accepted that the epithelium arises from all three germ layers.

Basement lamina consists of two layers - 
(a) BASAL LAMINA - Toward epithelium and its is made up of glycoprotein, which is secreted by epithelium cells.
(b) FIBROUS LAMINA - Towards connective tissue, in which collagen and reticular fibres are suspended in muccopolysaccharide which is matrix of connective tissue. Muccopolysaccharide is presented in the form of hyaluronic acid.

Simple columnar epithelium
Cells are elongated and column-shaped. Their nuclei are elongated and are usually located near the base of the cells.
Columnar epithelium is found in the following:
The lining of the stomach and intestines.
Some columnar cells are specialized for sensory reception such as in the nose, ears and the taste buds of the tongue.
Also have surface modifications such as cilia and microvilli and
Goblet cells (unicellular glands) are found between the columnar epithelial cells of the duodenum.
Function: secretion and absorption.

Squamous epithelial cells have the appearance of thin, flat plates. The shape of the nucleus usually corresponds to the cell form and helps to identify the type of epithelium. Squamous cells, for example, tend to have horizontal flattened, elliptical nuclei because of the thin flattened form of the cell. They form the lining of cavities such as the mouth, blood vessels, heart and lungs and snake up the outer layers of the skin. 
 

They are found in lining of mouth cavity, tongue, pharynx, oesophagus and vagina. Keratinized stratified epithelium- This tissue is found on outer dry surfaces of body like skin, hair claws and nails. The outer surface layer consists of deadepithelial cells.

Ciliated epithelium performs the function of moving particles or fluid over the epithelial surface in such structures as the trachea, bronchial tubes, and nasal cavities. 

A ciliated columnar epithelium lines the lumen of the uterine tube, where currents generated by the cilia propel the egg cell toward the uterus. They are also present in the buccal cavity of frog.

Simple cuboidal epithelium consists of a monolayer of epithelial cells that appear to be square-shaped in cross section. With large, rounded, centrally located nuclei, all the cells of this epithelium are directly attached to the basement membrane.
A monolayer of cuboidal epithelial cells covers the ovary and forms the ovarian surface epithelium. It plays a role in repairing the damage caused during every ovulation event and may also support the formation of an ovum.

Epidermis of the skin of vertebrates comprises stratified epithelium. Stratified epithelia are cover the exterior body surfaces and lining portions of the body tracts, where friction occurs. A multilayered epithelium allows deeper cells to replace the most superficial cells, as they are damaged or cast off from the epithelial surface.

Tessellated epithelium is another term used for simple squamous epithelium also called pavement epithelium due to its flat appearance. It is mainly present in the alveoli and blood capillaries and performs the function of diffusion.

Correct Answer :- D (pseudostratified columnar epithelium)

Explanation : Larynx is lined by ciliated pseudostratified columnar epithelium except vocal cords (lined by stratified squamous epithelium). The wall of larynx is reinforced by cartilage tissue. Large cartilages (cartilago thyroidea, cartilago cricoidea) and part of cartilago arytenoidea are composed of hyaline cartilage.

Germinal epithelium : Specialized cuboidal cells capable of producing gametes as found in gonads. Germinal epithelium produces gametes e.g., ova (Female gametes) and sperms (Male gametes)