TYPES OF TISSUES

Question 1

Definition of tissue

Answer 1

Tissue - a group of similar cells that work together to perform a common function.

There are 4 types of tissues in the human body:

1. Epithelial.
2. Muscle.
3. Connective.
4. Nerves.

Question 2

Epithelial Tissues

Answer 2

Tissues that cover the surfaces and lines internal cavities of the body.

There are two types of epithelia:

1. Simple.
2. Stratified.

Functions:

1. Protections – like skin that acts as barrier.
2. Secretion and filtration – like ones that secretes substances into kidneys tubules.
3. Absorption – like in the digestive tract that absorbs nutrients.
4. Sensation – like skin in touch.

Question 3

Simple Epithelium (one layer of cells):

Answer 3

Simple epithelium is composed of a single layer of cells. Due to it thinness, it is found in places of absorption and filtration.

Types:
* Squamous – flat cells involved in the diffusion of molecules. Can be found in capillaries and lung
alveoli.
* Cuboidal – cubed cells involved in secretion. Can be found in kidney tubules and salivary glens.
* Columnar – rectangle cells involved in secretion and absorption of molecules. Can be found in the
stomach and the small intestine.
*Pseudostratified – somewhat rectangle cells involved in protection. Can be found in respiration
system.

**All simple epithelium are found in places of exchange of material.

Question 4

Stratified Epithelium (composed of at least two layers of cells) used mainly for protection and separation

Answer 4

Stratified Epithelium is composed of many layers of cells. Due to its thickness, it is found in place that need
protection.
* Stratified Squamous – flat cells that protect against abrasion. Can be found in the mouth,
esophagus and the vagina.
* Stratified Cuboidal – cubed cells of at least two layers of cuboidal that provide protection. Can be
found in the ductal part of sweat and salivary glens.
* Stratified Columnar – rectangle cells that secrete and protect. Can be found in male urethra.
* Transitional Epithelia (allows stretching) – can be found in the bladder.

**Another classification of stratified squamous epithelia:
1. Keratinized – found in the human skin. Contains no nucleus or cytoplasm, and is basically a
membrane containing keratin (intermediate filament). 2. Non-keratinized – everywhere else there is stratified squamous that is not keratinized.

Question 5

Muscle Tissues

Answer 5

All muscle cells can contract. There are three types of muscle cells:

• Smooth
• Cardic
• Skeletal

Question 6

Smooth muscle tissue

Answer 6

Smooth – spindle shaped, and they are found in internal organs and blood vessels. Their
movement is relatively slow and involuntary.

*peristatic motion – a continues contraction of a duct achieved by smooth muscles in its wall. We find this type of motion in the digestive system, the urinary system and in the spermatic cord.
Smooth muscles can regenerate quite efficiently.

Question 7

Skeletal muscle tissue

Answer 7

The cells are shaped in a cylindrical fashion. They have striated architecture; they have
multiple nuclei. Multiple nuclei located in the periphery. They can regenerate rapid forceful
contraction. They are voluntary and composed of red aerobic fibres and white anaerobic fibres.
They have minimal ability to regenerate.

*striated architecture – A muscle that is made up of long fibre characterized by transverse or
oblique striations, or alternating light and dark bands under the microscope.

*syncytium – multinuclear cell.

Question 8

Cardiac muscle tissue

Answer 8

has a striated architecture. Has one to two nuclei interact involuntarily and have a special
structure called intercalated disc which is composed of gap junctions. Has no ability to regenerate.

Question 9

Connective Tissues

Answer 9

Proper connective tissue. Provides structure and support to the body. Connects different tissues and organs. The predominant cell is called fibroblast - these cells have a great ability to regenerate and are capable of secreting collagen (the most common extracellular fibre).

Question 10

Components of connective tissue

Answer 10

1. Fibres – provide strength, elasticity and support (not found in blood).
    Collagenous – made of protein called collagen
   and is the most abundant fibre (found in
   tendons, ligaments and skin)
    Elastic – made of protein called elastin (thinner
   than collagen) and can be stretched or
   snapped back.
2. Ground substance – a gel that surrounds cell and extracellular matrix (protein and sugar).
3. Cells – dispersed throughout the connective tissue. Fibroblasts are the cells that synthesis the 𝐸𝐶𝑀.

Question 11

Loose connective tissues

Answer 11

mostly found around structures. For instance, the outermost layer of blood vessels. This type of tissue contains many cells, a loose arrangement of fibres, and
moderately viscous fluid matrix. It cushions organs and provide support, but permits independent movement. Found beneath dermis of skin, digestive tract, respiratory and urinary tracts, between muscles, around blood vessels, nerves and joints.

Question 12

Dense connective tissues

Answer 12

mostly found between structures. This type of tissue contains a dense woven network of collagenous fibres in a viscous matrix. It is found in joint capsules, in the
tendons, in the connective tissue that envelops muscles (muscle fascia), and it forms dermis of the
skin. It is impact resistant. It provides firm attachment and reduces friction between muscle, stabilized positions of bones and prevents overexpansion of organs like the bladder.

Question 13

Reticular connective tissues

Answer 13

found insides of organs. For instance, the liver. Network of reticular
collagen fibres that forms a soft skeleton that support organs and cells.

Question 14

Cartilage( connective tissue)

Answer 14

found in growing bones, joints, nose, ears and more… Composed of chondrocytes that
produce proteoglycans and collagen. Cartilage does not contain blood vessels and does not
regenerate.

Question 15

Bone (connective tissue)

Answer 15

Bone is made out of three types of cells:

1. Osteoclasts (destroy the bone).
2. Osteoblasts (build the bone).
3. Osteocytes (retired osteoblasts – cells in the bond).

The outer most component of the bone is called “the compact bone”, which is made out of
osteons. Inner to it, we have the “trabecular bone” which is built like a spider web, and there we
find the “red bone marrow”. In long bones, there is a central medullary canal which in adults is
filled with yellow bone marrow instead of red.

Question 16

Adipose(connective tissue)

Answer 16

made out of adipocytes. White adipocytes store 𝑇𝐴𝐺 and cholesterol, while brown adipocytes generate heat. Specialized in sorting fat, protecting and cushioning organs, insulation of temperature. Made out of adipocytes that are up to 20% of the body’s mass.

Question 17

Blood(connective tissue)

Answer 17

contains 55% plasma (92% 𝐻2𝑂, 7% sugar, salts, hormones, albumin etc.), and 45% cells:

1. Erythrocytes (𝑅𝐵𝐶) – don’t have a nucleus, and are filled with haemoglobin that carries oxygen and nutrients to cells in the body. 𝑅𝐵𝐶 lives for around 120 days.
2. Thrombocytes (platelets) – important for blood clothing.
3. Leucocytes (WBC) – part of the immune system.

*all blood cell originates in the red bone marrow.
*Albumin - a very big protein that is part of the plasma and is important for fluid distribution in the
blood and bud.

Question 18

Nervous Tissues

Answer 18

Nervous tissue forms the nervous system which through a network of nerves is responsible for coordinating the movement of the body.

Question 19

Types of nerve cells

Answer 19

1. Neurons – transmit electrochemical signal. Basic structural unit of the nervous system. Structure:
   * Cell body (soma) – contains organelles.
   * Dendrites – branched structures meant for receiving information and transmitting it to
   the cell body.
   * Axon – nerve fibre that is specialized to carry an electrical message.
   * Synapse – space between neurons that allows for message transmission.
2. Glial cells – provides support and nutrients to the neurons (oligodendrocytes and Schwann cells
   isolate neurons or can anchor them to blood vessels).