Chapter 3- Cells and tissues Flashcards

1
Q

what are cells

A

cells are the structural units of all living things

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2
Q

What is a generalised cell?

A

A generalised cell is a cell that contains the three main regions or parts, the nucleus, cytoplasm and plasma membrane.

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3
Q

Describe the structure of the plasma membrane?

A

The plasma membrane consists of two phospholipids (fats) layers that are arranged “tail to tail” with cholesterol and floating proteins scattered among them. Some phospholipids also have sugar groups attached to them, to form glycolipids. The phospholipid bilayer contains polar heads called hydrophilic “water loving” and nonpolar “tails” called hydrophobic “water fearing”

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4
Q

What are the functions of the proteins in lipid layer of the plasma membrane

A

Some proteins are enzymes
Most are receptors for hormones/other chemical messengers
Binding sites for anchoring the cell
Most protein are involved in transport
Some cluster together to form protein channels for water soluble molecules or ions to move
Others act as carriers that bind to a substance and move it through the membrane
Some act as receptors for bacteria, viruses or toxins can bind to
Some determine your blood type
Play a role in cell recognition and interactions

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5
Q

How are cells bound together

A

Glycoproteins in the glycocalyx act as an adhesive or cellular glue.
2. Wavy contours of the membranes of adjacent cells fit together in a tongue-and-groove fashion.
3. Special cell membrane junctions are formed (Figure 3.2). These junctions
vary structurally depending on their roles

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6
Q

What are the functions of tight junctions

A

Tight junctions are impermeable junctions that encircle the cells
and bind them together into leak proof sheets. The adjacent plasma membranes
fuse together tightly together like a zipper, which prevents substances from passing
through the extracellular space between the cells.

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7
Q

Give an example of a tight junction

A

An example would be in the small intestine, the junctions prevent digestive
enzymes from leaking into the bloodstream.

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8
Q

What are the functions of desmosomes

A

Desmosomes are anchoring junctions that are scattered like rivets
along the sides of adjacent cells. They prevent cells subjected to mechanical stress
(such as heart muscle cells and skin cells) from being pulled apart. These junctions
are buttonlike thickenings of adjacent plasma membranes (plaques) that are
connected by fine protein filaments

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9
Q

What are the functions of gap junctions

A

The main function of gap junctions is communications. These
junctions are mainly found in the heart and between embryonic cells. In gap
junctions the neighbouring cells are connected by hollow cylinders composed of
proteins (called connexons) that span the entire width of the abutting membranes.

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10
Q

Why do phospholipids (which form the bulk of plasma membranes) organize
into a bilayer, tail to tail, in a watery environment?
,

A

The phospholipids have both polar (heads) and non polar (tails) regions.
Polar aligns with polar (water and other polar molecules inside and outside the cell).
Non polar aligns with non polar in the membrane interior.
The external faces of some membrane proteins have sugar groups attached to them

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11
Q

what are 3 roles these sugar-coated proteins play in the life of a cell?

A

They act as receptors, determine blood type, and play a role in cell-to-cell interactions.

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12
Q

What are the functions of the nucleus

A

The nucleus is the control center of the cell.
● The genetic material (DNA- Deoxyribonucleic acid) is stored in the nucleus of
the cell, it contains all the instructions needed for the building of the whole
body.
● DNA has genes, which carry the instructions for building proteins.
● DNA is also necessary for cell reproduction.
● The nucleus forms the shape of the cell.
● The nucleus has three recognisable regions or structures

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13
Q

What are the three regions or structures of the nucleus

A

Nucleolus
chromatin
Nuclear envelope

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14
Q

What are the functions of the nuclear envelope

A

The nuclear boundary is a double membrane barrier which is called the nuclear envelope or nuclear membrane.
● At various points the two layers of the nuclear envelope fuse, generating openings called nuclear pores.
● The nuclear envelope allows some but not all substances to pass through it,
through the relatively large nuclear pores in the nuclear envelope.
● The nuclear membrane encloses a jelly-like fluid which is called the neoplasm in which other nuclear elements are suspended.

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15
Q

What are the functions of the nucleolus

A

Nucleoli is plural for nucleolus. Nucleoli are the sites where cell structures
called ribosomes are assembled.

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16
Q

What are the functions of the chromatin

A

When a cell is not dividing, its DNA is carefully wound around proteins called
histones to form a loose network of “beads on a string” called chromatin.
● Chromatin is scattered throughout the nucleus.
● When a cell divides by mitosis to form two daughter cells, the chromatin
condenses to form dense, rod-like bodies called chromosomes.

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17
Q

What are the three main components of the cytoplasm

A

Cytosol
Inclusions
Organelles

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18
Q

What is the cytosol

A

The cytosol is a semi- transparent fluid that suspends the other elements.
Dissolved in the cytosol, which is largely water, nutrients and a variety of
other solutes.

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19
Q

What are inclusions

A

Are chemical substances that may or may not be present, depending on the cell type.
● Most inclusions are stored nutrients or cell products floating in the cytosol.
● They include the lipid droplets common in fat cells, glycogen granules
abundant in liver and muscle cells, pigments such as melanin in skin and hair
cells, mucus and other secretory products and various kinds of crystals.

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20
Q

What are the functions of the mitochondria?

A

“Powerhouses” of the cell
Change shape continuously
Carry out reactions where oxygen is used to break down food
Provides ATP for cellular energy
Site of aerobic respiration
ATP Synthesis

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21
Q

What are the functions of the ribosomes?

A

The site of protein synthesis

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22
Q

What are the two locations in the cell where ribosomes are found

A

Free in the cytoplasm
As part of the rough endoplasmic reticulum

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23
Q

What are the functions of the Rough ER?

A

The proteins that are made on the ribosomes which are on the rough ER migrate into the rough ER tunnels.
Rough ER is abundant in cells that make (synthesise) and export (secrete) proteins.

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24
Q

What are the functions of the Smooth ER?

A

The smooth endoplasmic reticulum plays no role in protein synthesis, because it
does not have ribosomes.

The main function of the smooth ER is lipid metabolism and detoxification of drugs and pesticides.

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25
Q

What are the functions of the Golgi Apparatus?

A

Its major function is to modify, package, and ship proteins (sent to it by the
rough ER via transport vesicles) in specific ways, depending on their final
destination
It also packages hydrolytic enzymes into membrane- bound organelles
called lysosomes that remain in the cell

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26
Q

What are the functions of the Lysosomes?

A

They are membranous “bags” containing powerful digestive enzymes.
Contain enzymes that digest worn-out or non-usable materials within the cell

Site of intracellular digestion. the stomach of the cell

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27
Q

What are the functions of the Peroxisomes?

A

Peroxisomes are membranous sacs containing powerful oxidase enzymes
that use molecular oxygen (O2) to detoxify a number of harmful or poisonous
substances, including alcohol and formaldehyde.
● Their most important function is to disarm dangerous free radicals
they replicate themselves by pinching in half

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28
Q

What are free radicals

A

Free radicals are highly reactive chemicals with unpaired electrons that can damage the structure of proteins and nucleic acids.

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29
Q

What is the cytoskeleton

A

The cytoskeleton is an elaborate network of protein structures that extend throughout the cytoplasm. This acts as the cells “bones or muscles” by furnishing an internal framework that determines cell shape, supports other organelles and
provides the machinery for intracellular transport and various types of cellular
movements.

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30
Q

what is the cytoskeleton made up of

A

Microtubules
Microfilaments
Intermediate filaments

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31
Q

What is the function of the Microfilaments and give an example

A

an example of microfilaments are actin and they are
mostly involved with the cells motility and in producing the changes in the cell shape.
transport of cell products throughout the cytoplasm

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32
Q

What is the function of the microtubules and give an example

A

They determine the overall shape of a cell and the distribution
of organelles. These structures are very important for cell division.
make up cilia and flagella.
they help with tansport of substances within. the cell

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33
Q

What is the function of the intermediate filaments and give an example

A

They help to form the desmosomes and
provide the internal guy wires to resist pulling forces on the cell.
gives the cell structural support
resists mechanical stress

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34
Q

what are the functions of the centrioles

A

Centrioles are best known for their role in generating microtubules and
directing the formation of the mitotic spindle during cell division.

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35
Q

what are flagella and where is it found

A

Are cilia projections that are longer found on a sperm cell

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36
Q

what are cilia and where is it found

A

Are whiplike cellular extensions that move substances along the cell surface.
For example mucus is carried up and away from the lungs on the ciliated cells lining
the respiratory system,

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37
Q

what are microvilli

A

Microvilli are tiny, fingerlike extensions of the plasma membrane that project from
an exposed cell surface. They increase the cells surface area tremendously and are
usually found on the surface of cells during active absorption such as the intestinal
and kidney tubule cells.

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38
Q

what are the different Cells that connect body parts and where are they found in the body.

A

Fibroblast- secretes cable like fibers
Erythrocyte (Red Blood cells)- this cell carries oxygen in the blood

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39
Q

what are the different Cells that cover and line body organs

A

Epithelial cells

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40
Q

what are the different Cells that move organs and body parts

A

Smooth, cardiac and muscle cells

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41
Q

what are the different Cells that store nutrients

A

Fat cells

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42
Q

What are the different Cells that fight disease

A

White blood cells

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43
Q

What are the Cells that gather information and
control body functions

A

Nerve cells

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44
Q

Define selectively permeable

A

Selective permeability means that a barrier allows some substances to pass
through it while excluding the others

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45
Q

what is a solution

A

A solution is a homogenous mixture of two or more components, for example
the air we breathe is a mixture of gases, seawater is a mixture between salt
and water etc

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46
Q

what is a solvent

A

The substance that has the largest amount is called the solvent (or
dissolving medium).

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47
Q

what is a solute

A

Components or substances that are present but in smaller amounts

48
Q

define diffusion

A

Diffusion is the process by which molecules and ions move away from
areas where they are more concentrated (with fewer of them). Diffusion is the
process of molecules by which they move from a high concentration to a low
concentration.

49
Q

what are the two types of diffusion

A

faciliated and simple

50
Q

what is intracellular fluid

A

Intracellular fluid (nucleoplasm and the cytosol) is a solution that contains
small amounts of gases (Oxygen and Carbon dioxide), nutrients and salts
that are dissolved in water.

51
Q

define osmosis

A

is the diffusion of water through a selectively permeable membrane such
as the plasma membrane, because water is highly polar, it is repelled by the
(NonPolar) lipid core of the plasma membrane, but it can and does pass easily
through special pores called aquaporins created by proteins in the membrane.

52
Q

what is extracellular fluid

A

The extracellular fluid or interstitial fluid is the fluid that continuously bathes
the exterior of our cells

53
Q

what are two types of passive processes

A

Diffusion
Filtration

54
Q

The hydrophobic core of the plasma membrane is a typical barrier to diffusion.
Molecules will only diffuse through the plasma membrane if:

A

● The molecules are small enough to pass through the membranes pores
(channels formed by membrane proteins)
● The molecules are lipid-soluble
● The molecules are assisted by a membrane carrier.

55
Q

what is faciliated diffusion

A

facilitated diffusion provides a
passage for certain needed substances (notably glucose) that are both
lipid-insoluble and too large to pass through the membrane pores, or charged

56
Q

what is filtration

A

is the process by which water and solutes are forced through a
membrane or capillary wall by fluid or hydrostatic pressure
gradient is involved
The gradient is a pressure gradient that actually pushes solute-containing fluid (filtrate)
from the higher pressure areas through the filter to the lower pressure area.
Filtration is not very selective, only
blood cells and protein molecules too large to pass through the membrane pores
are held back.

57
Q

when does the cell need to use active transport

A

This Happens When a cell uses ATP to move substances across the membrane,
Substances moved actively are usually unable to pass in the desired direction by diffusion. They may be too large to pass through membrane channels,
the membrane may lack special protein carriers for their transport and may not be able to dissolve in the fat core, or they may have to move “uphill”
against their concentration gradients.

58
Q

what are the two most important active processes

A

Active transport (solute pumping) or Vesicular transport

59
Q

what is a solute pump

A

it is a protein carrier involved in active transport

60
Q

Describe the sodium potassium pump

A

the sodium potassium pump alternatively carries potassium ions and sodium ions in and out of the cell. there are more sodium ions outside the cells than inside, so some tend to remain inside the cell unless the cell uses ATP to force them out.
ATP is split into ADP and p (inorganic phosphate) and the phosphate is then attached to the sodium potassium pump in a process called phosphorylation
There are more potassium ions inside cells than in the extra-cellular fluid,
and potassium ions that leak out of cells must be actively pumped back
inside.
Because each of the pumps in the plasma membrane transports only
specific substances, active transport provides a way for the cell to be very
selective in cases where substances cannot pass by diffusion. (No
pump—no transport.)

61
Q

describe vesicular transport

A

Some substances cannot get through the plasma membrane by active or
passive transport.
● Vesicular transport, involves help from ATP, to fuse or separate membrane
vesicles and the cell membrane, it moves substances into or out of cells “in
bulk” without their actually crossing the plasma membrane directly.

62
Q

what are the two types of vesicular transport

A

Exocytosis
Endocytosis

63
Q

what is Exocytosis

A

“out of the cell”

is the mechanism that cells use to actively
secrete hormones, mucus, and other cell products or to eject certain cellular
wastes.

64
Q

What is Endocytosis

A

“into the cell”

which includes those ATP-requiring processes
that take up, or engulf, extracellular substances by enclosing them in a
vesicle

65
Q

what is phagocytosis

A

“Cell eating”

Certain white blood cells, such as the macrophage, and other “professional”
phagocytes of the body act as scavenger cells that police and protect the
body by ingesting bacteria and other foreign debris.

66
Q

what is pinocytosis

A

“Cell Drinking”

during which the cell “gulps” droplets of
extracellular fluid.

67
Q

what is receptor mediated endocytosis

A

is the main cellular mechanism for taking up specific target molecules

68
Q

explain DNA replication

A

The precise trigger for DNA replication is
unknown but once it starts, it continues until
all the DNA has been replicated.
● The two strands of the double helix structure
of the DNA unwinds.
● The weak hydrogen bonds between
nitrogenous bases of each complementary
base pair break and the two DNA strands
unzip/separate.
● Each DNA –strand serves as a template on
which its complement is built.
● Free-floating nucleotides in the nucleoplasm
of the nucleus, attach to their
complementary nitrogenous bases (A to T& C to G)
● This results in two identical DNA molecules.
Each molecule consists of one original
strand and one new strand.§

69
Q

what is mitosis

A

is the process of dividing a nucleus into two daughter nuclei with exactly
the same genes as the “mother” nucleus.

70
Q

describe prophase of mitosis

A

● the chromatin threads begins to coil and shorten so that it becomes visible under a microscope.
● Because DNA has already been replicated,
(each chromosome is actually made up of two identical
strands called sister chromatids; they are held
together by a small button-like body called a
centromere).
● The centrioles separate from each other and begin to
move toward opposite sides of the cell, directing the assembly of a mitotic spindle
(composed of microtubules) between them as they move.
● By the end of prophase, the nuclear envelope and the
nucleoli have broken down and temporarily
disappeared
● the chromosomes have attached randomly to the spindle fibers by their centromeres.

71
Q

describe metaphase of mitosis

A

In this short stage, the chromosomes line up at the
metaphase plate (the center of the spindle midway
between the centrioles) so that a straight line of
chromosomes is seen.

72
Q

describe Anaphase of mitosis

A

● During anaphase, the centromeres that have
held the chromatids together split.
● The chromatids (now called chromosomes
again) begin to move slowly apart, drawn toward
opposite ends of the cell.
● This careful division of sister chromatids ensures that each daughter cell gets one copy of every chromosome.
● Anaphase is over when the chromosomes stop moving.

73
Q

describe Telophase of mitosis

A

Telophase is essentially prophase in reverse.
● The chromosomes at opposite ends of the
cell uncoil to become threadlike chromatin
again.
● The spindle breaks down and disappears,
a nuclear envelope forms around each
chromatin mass, and nucleoli appear in
each of the daughter nuclei.
● Centriole replication is deferred until late interphase of the next cell cycle, when
DNA replication begins before the onset of mitosis

74
Q

Describe cytokinesis

A

Is the division of the cytoplasm, which usually begins late anaphase and completes during telophase.
A contractile ring made of microfilaments forms a cleavage furrow over the midline of the spindle, and it eventually squeezes, or pinches, the original cytoplasmic
mass into two parts.
● Thus, at the end of cell division, two daughter cells exist. Each is smaller with less cytoplasm than the mother cell had but is genetically identical to the mother cell.

75
Q

what are enzymes

A

biological catalysts that speed up
every chemical reaction that occurs in cells), are functional proteins.

76
Q

what is a gene

A

A gene is defined as a DNA segment that carries the information for building
one protein.

77
Q

what are the three types of RNA used in protein synthesis

A

● Ribosomal RNA (rRNA) helps form the ribosomes, where proteins are built.
● Messenger RNA (mRNA) molecules are long, single nucleotide strands that
resemble half of a DNA molecule. They carry the “message” containing
instructions for protein syn- thesis from the DNA (gene) in the nucleus to the
ribosomes in the cytoplasm.
● Transfer RNA (tRNA) molecules are small, cloverleaf-shaped molecules
that escort amino acids to the ribosome.

78
Q

describe transcription

A
  • The double helix DNA unwinds.
  • The double-stranded DNA unzips/weak hydrogen bonds break
  • to form two separate strands.
  • One strand is used as a template
  • to form mRNA
  • using free RNA nucleotides from the nucleoplasm.
  • The mRNA is complementary to the DNA.
  • mRNA now has the coded message for protein synthesis.
  • mRNA moves from the nucleus to the cytoplasm and attaches to the ribosome
79
Q

describe translation

A
  • Each tRNA carries a specific amino acid.
  • When the anticodon on the tRNA
  • matches the codon on the mRNA
  • then tRNA brings the required amino acid to the ribosome.
  • Amino acids become attached by peptide bonds
  • to form the required protein
80
Q

what is histology

A

histology is the study of body tissues

81
Q

what is a tissue

A

A tissue is a group of cells with similar specialized structure and carry out specific
functions

82
Q

what are the 4 main types of tissues

A

epithelial
connective
muscle
nervous

83
Q

what is epithelial tissue

A

Epithelial tissue, or epithelium, is the lining, covering, and glandular tissue of
the body.
epithelium covers all free body surfaces, both inside and out, and contains versatile cells.
epithelium forms the boundaries that separate us from the outside

84
Q

What are the 4 functions of epithelium

A

● Protection
● Absorption
● Filtration
● Secretion

85
Q

what are the locations of epithelial tissue

A

Body coverings
Body linings
Glandular tissue

86
Q

what are the characteristics of epithelium
(CALAR)

A

Cells fit closely together and often form sheets
The apical surface is the free surface of the tissue
The lower surface of the epithelium rests on a basement membrane
Avascular (no blood supply)
Regenerate easily if well nourished

87
Q

where is Simple squamous epithelium found in the body

A

This type of epithelium usually forms membranes where filtration or exchange of substances by rapid diffusion occurs.
This type of epithelium is found in the air sacs of the lungs (alveoli) and forms the walls of the capillaries. It also forms serous membranes or serosae

88
Q

where is Simple cuboidal epithelium found in the body

A

It is common in glands and their associated small tubes called ducts.
it forms the walls of the kidney tubules and covers the surface of the ovaries.

89
Q

where is Simple columnar epithelium found in the body

A

Simple columnar epithelium lines the entire length of the digestive tract from the stomach to the anus.
Epithelial membranes that line body cavities open to the body exterior are called mucosae, or mucous membranes.

90
Q

where is Pseudostratified epithelium
(pseudostratified ciliated columnar epithelium) found in the body

A

It gives the false impression that it is stratified
This variety mainly functions in absorption and secretion
lines most of the respiratory tract

91
Q

where is Stratified squamous epithelium found in the body

A

Stratified squamous epithelium is found in sites that receive a good deal of abuse or friction, such as the surface of the skin, the mouth, and the oesophagus

92
Q

where is Stratified cuboidal epithelium found in the body

A

Very rare in the body and is mostly found in the ducts of large glands

93
Q

where is Stratified columnar epithelium found in the body

A

Mucous membrane (conjunctiva) lining your eyelids
Pharynx
Anus

94
Q

where is Stratified Cuboidal and Columnar found in the body

A

Very rare in the body and is mostly found in the ducts of large glands

95
Q

where is Transitional epithelium found in the body

A

that forms the lining of only a few organs—the urinary bladder, the ureters, and part of the urethra.
In the bladder, the ability of transitional epithelium to stretch allows more urine to be stored without increasing pressure in the bladder.

96
Q

where are Glandular epithelium found in the body

A

Found in Exocrine and Endocrine glands

97
Q

what are the functions of connective tissue

A

Connective tissues perform many functions, but they are primarily involved in
protecting, supporting, cushioning, and insulating other body tissues.

98
Q

what are the characteristics of connective tissue
(BVAEM)

A

Variations in blood supply
Some tissue types are well vascularized
Some have a poor blood supply or are avascular
Extracellular matrix
Non-living material that surrounds living cells

99
Q

Where is the connective tissue Bone
(osseous tissue) found in the body

A

Is composed of osteocytes sitting in cavities called lacunae.
These pits are surrounded by layers of a very hard matrix that contains calcium salts in addition to large numbers of collagen fibers.
Because of its rocklike hardness, bone has an exceptional ability to protect and support other body organs (for example, the skull protects the brain).

100
Q

where is Hyaline cartilage found in the body

A

Its major cell type is chondrocytes (cartilage cells).
It is found in only a few places in the body.
Most wide- spread is hyaline cartilage, which has abundant collagen fibers hidden by a rubbery matrix with a glassy, blue-white appearance.
It forms the trachea, or windpipe, attaches the ribs to the breastbone, and covers bone ends at joints.
The skeleton of a fetus is made largely of hyaline cartilage; but by the time the baby is born, most of that cartilage has been replaced by bone.

101
Q

where is Fibro cartilage found in the body

A

forms the cushion like disks between the vertebrae of the spinal column
It is a tough, slightly flexible, supporting tissue.
It is found as pads called the intervertebral discs between the bodies of vertebrae.
It is found between the articulating surfaces of the bones of the knee joint called semilunar cartilages
It is found on the rim of the bony sockets of the hip and shoulder joints

102
Q

where is Elastic cartilage found in the body

A

Elastic cartilage is found in structures with elasticity, such as the external ear
It provides support and maintains the shape of, for example, the pinna or lobe of the ear, the epiglottis and part of the tunica media of blood vessel walls.

103
Q

where is Dense connective tissue found in the body

A

It is also called dense regular fibrous tissue, collagen fibers are the main matrix element
Dense regular connective tissue forms strong, ropelike structures such as tendons (Tendons attach skeletal muscles to bones) and ligaments (ligaments connect bones to bones at joints) that withstand tension in one direction.
makes up the lower layers of the skin (dermis), where it is arranged in sheets and withstands tension in many directions

104
Q

what are the four main types of loose connective tissue

A

The main types of loose connective tissues are:
○ Areolar
○ Adipose
○ Retricular
○ Blood

105
Q

where is Areolar connective tissue found in the body

A

A soft layer of areolar connective tissue called the lamina propria underlies all mucous membranes. Its fluid matrix contains all types of fibers, which form a loose network.It is a type of loose connective tissue Areolar tissue is also found in or around mucous membranes, and around blood vessels, nerves, and the organs of the body.

106
Q

where is Adipose Connective Tissue found in the body

A

Adipose tissue is commonly called fat.
Adipose tissue forms the subcutaneous tissue beneath the skin, where it insulates the body and protects it from bumps and extremes of both heat and cold. Adipose tissue also protects some organs individually—the kidneys are surrounded by a cap- sule of fat, and adipose tissue cushions the eyeballs in their sockets.
There are also fat “depots” in the body, such as the hips, breasts, and belly, where fat is stored and available for fuel if needed.

107
Q

where is Reticular connective tissue found in the body

A

Reticular tissue is limited to certain sites: It forms the stroma (literally, “bed” or “mattress”), or internal frame- work of an organ.
The stroma can support many free blood cells (largely white blood cells called lymphocytes) in lymphoid organs such as lymph nodes, the spleen, and bone marrow

108
Q

describe the tissue Blood

A

Also called vascular tissue
It is considered a connective tissue because it consists of blood cells surrounded by a nonliving, fluid matrix called blood plasma.
The “fibers” of blood are soluble pro- teins that become visible only during blood clotting.
Blood is the transport vehicle for the cardiovascular system, carrying nutrients, wastes, respiratory gases, white blood cells, and many other substances throughout the body.

109
Q

what is the function of skeletal muscle

A

to produce movement

110
Q

what are the three types of muscle tissue

A

Skeletal tissue
Cardiac tissue
Smooth tissue

111
Q

Describe skeletal tissue

A

Skeletal muscle tissue is packaged by connective tissue sheets into organs called skeletal muscles, which are attached to the skeleton.
Muscle tissue are tissue controlled voluntarily
Contracts to pull on bones or skin
Produces gross body movements or facial expressions

112
Q

what are the characteristics of skeletal muscle tissue

A

The cells of skeletal muscle are long, cylindrical, and multinucleate (more
than one nucleus), and they have obvious striated (stripes).
skeletal muscle cells are elongated to provide a long axis for contraction,
they are often called muscle fibers.

113
Q

describe cardiac tissue

A

The cardiac muscles are only found in the heart wall
As it contracts, the heart acts as a pump to propel blood through the blood
vessels.
Cardiac muscle has striations
cardiac cells have only a single nucleus and are relatively short, branching
cells that fit tightly together (like clasped fingers) at junctions called
intercalated discs. These intercalated discs contain gap junctions that allow
ions to pass freely from cell to cell.
Cardiac muscle is under involuntary control, which means that we cannot
consciously control the activity of the heart.

114
Q

describe smooth muscle tissue

A

Smooth muscle have no striations. The individual cells have a single nucleus
and are tapered at both ends.
43
● Smooth muscle is found in the walls of hollow organs such as the stomach,
uterus, and blood vessels.
● As smooth muscle in its walls contracts, the cavity of an organ alternately
becomes smaller (constricts when smooth muscle contracts) or enlarges
(dilates when smooth muscle relaxes) so that substances are mixed and/or
propelled through the organ along a specific pathway.
● Contractions of smooth muscle are longer and slower than the other two
muscle types. Peristalsis, a wavelike motion that keeps food moving through
the small intestine, is typical of its activity.

115
Q

what is nervous tissue

A

Nervous tissue is composed of Neurons, which send and receive electrochemical impulses
from one part of the body to another. Thus irritability and conductivity are the teo major
functional characteristics.