Structural Organisation in Animals Flashcards
what is a tissu
a group of similar cells along with intercellular substances/matrix to perform a specific function. These cells may or may not be similar in nature/structure/function but their origin is always the same.
what is an organ
when tissues are organised in specific pattern and proportion, an organ is formed
what is an organ system
when 2 or more organs perform a common function by their physical/chemical interaction, they form an organ system
what are 4 types of animal tissues and their basic functions
(i) epithelium-lining/covering and protection(origin: endoderm/mesoderm/ectoderm)
(ii) Connective- connection, transport and support to body(origin: mesoderm)
(iii) muscular- help in contractionand relaxation which give rise to mvmnt and locomotion(origin: mesoderm with exceptions)
(iv) generate and conduct nervous impulses.( origin: ectoderm)
THESE ARE DIVIDED BASED ON STRUCTURE AND FUNCTION ONLY
what are intercellular junctions
specialised junctions provide both structural
and functional links between its individual cells. Three types of cell junctions
are found in the epithelium and other tissues. These are called as tight,
adhering and gap junctions. Tight junctions help to stop substances
from leaking across a tissue. Adhering junctions perform cementing to
keep neighbouring cells together. Gap junctions facilitate the cells to
communicate with each other by connecting the cytoplasm of adjoining
cells, for rapid transfer of ions, small molecules and sometimes big molecules.
intro to epithelial tissue
This tissue has a free surface, which faces either a body fluid or the outside
environment and thus provides a covering or a lining for some part of the
body. The cells are compactly packed with little intercellular matrix.
types of epithelial tissue
There
are two types of epithelial tissues namely simple epithelium and
compound epithelium. Simple epithelium is composed of a single layer
of cells and functions as a lining for body cavities, ducts, and tubes. The
compound epithelium consists of two or more cell layers and has protective
function as it does in our skin.
what is simple squamous epithelium
The squamous epithelium is made of a single thin layer of flattened
cells with irregular boundaries. They are found in the walls of blood vessels
and air sacs of lungs and are involved in functions like forming a diffusion
boundary
what is simple cuboidal epithelium
The cuboidal epithelium is composed of a single layer of
cube-like cells. This is commonly found in ducts of glands and tubular
parts of nephrons in kidneys and its main functions are secretion and
absorption. The epithelium of proximal convoluted tubule (PCT) of
nephron in the kidney has microvilli.
what is simple columnar epithelium
The columnar epithelium is
composed of a single layer of tall and slender cells. Their nuclei are elongated and located
at the base. Free surface may have microvilli. They are found in the lining
of stomach and intestine and help in secretion and absorption.
what is ciliated epithelium
If the
columnar or cuboidal cells bear cilia on their free surface they are called
ciliated epithelium (Figure 7.1d). Their function is to move particles or
mucus in a specific direction over the epithelium. They are mainly present
in the inner surface of hollow organs like bronchioles and fallopian tubes.
what atwo types of glandular epithelium
Some of the columnar or cuboidal cells
get specialised for secretion and are called
glandular epithelium (Figure 7.2). They
are mainly of two types: unicellular,
consisting of isolated glandular cells (goblet
cells of the alimentary canal), and
multicellular, consisting of cluster of cells
(salivary gland).
what are endocrine and exocrine glands
On the basis of the mode of
pouring of their secretions, glands are
divided into two categories namely
exocrine and endocrine glands. Exocrine
glands secrete mucus, saliva, earwax, oil,
milk, digestive enzymes and other cell
products. These products are released
through ducts or tubes. In contrast,
endocrine glands do not have ducts. Their
products called hormones are secreted
directly into the fluid bathing the gland.
what is stratified epithelium
Compound epithelium is made of more than one layer (multi-layered) of cells and thus has a limited role in secretion and absorption (Figure 7.3). Their main function is to provide protection against chemical and mechanical stresses. They cover the dry surface of the skin, the moist surface of buccal cavity, pharynx, inner lining of ducts of salivary glands and of pancreatic ducts.
