Chapter 4.2.1 Introduction to Epithelial Tissues BIO201

Summary

هذا النص يناقش النسيج البيئي، الذي يُعرف أيضًا باسم ال表層، ويتكون من مجموعة من الخلايا المرفقة ببعضها البعض بقوة، وتغطي الأسطح والفراغات في الجسم. يُعتبر هناك نوعان رئيسيان لل表層: ال表層 المحيطة وال表층 الداخلة، ويوجد أيضًا ال表층 المخزنة، التي تغطي أنبوب الهياكل البيئية مثل المدخنات اللعابية والكبد. تتضمن ال表층 البيئية وظائف مثل الحماية وال امتصاص والتصفية والإخراج والإنتاج، ولديها خواص تميزها مثل الوجهية والاتصالات الخاصة والمدعمة من النسيج ال結蹄، ولديها قدرة عالية على التجدد.

Takeaways

• 🧬 الأنسجة ال表層ية، تُعرف أيضاً بـ'ال表層'، هي مجموعة من الخلايا التي تلتصق بقوة، وتغطي الأسطح الجسدية أو الحقول.
• 🔍 هناك نوعان رئيسيان من ال表層، ال表층 التغطية و ال表층 الملساء، تغطي الأسطح الخارجية مثل الجلد أو تملؤ الحقول الداخلية مثل المسار التنفسي أو القناة الهضمية.
• 💧 ال表층 البدنية هي ال表층 التي تغطي أنبوب البول، مثل بول اللسان أو بول الكبد، وتساهم في إخراج بعض ال排泄s.
• 🛡️ وظائف ال表층 الرئيسية هي الحماية، ال吸引力، الترشيح، الإخراج، والترشح، وبعضها تشارك في استقبال الحواس.
• 🌟 ال表층 ال表층ية لديها خواص مميزة خمسة: التوجهية، الاتصال الخاص، الدعم من الأنسجة ال結蹄، وعدم وجود الأوعية الدموية، والقدرة على التجديد.
• 📍 ال表층 ال表층ية هي 'لا تغذي' لأنها لا تتضمن الأوعية الدموية لكنها تحصل على التغذية من الdiffusion من ال结蹄 التحتية.
• 💢 ال表층 ال表층ية هي 'م.innervated' بمعنى أنها تتضمن العصب، مما يسمح لل表층 بالتعرف على المعلومات المختلفة في الجسم.
• 🔄 ال表층 ال表층ية لديها قدرة عالية على التجديد بسبب التعرض لعوامل تضرية يمكن أن تؤدي إلى الضرر، مما يتطلب استبدال الخلايا المدمرة بخلايا جديدة.
• 🔑 ال表층 ال表층ية يمكن تصنيفها بناءً على عدد طبقات الخلايا وشكل الخلايا، مثل ال表層 بسيط أو متعدد الطبقات، وال表層 مسطح أو مربع أو عمودي.
• 🔬 في ال表층 متعدد الطبقات، يمكن أن يختلف شكل الخلايا في كل طبقة، ويتم تصنيف ال表층 بناءً على شكل الخلايا في السطح العلوي لل表층.
• 📚 يمكن أن نرى مثالاً ل表層 بسيط مسطح، حيث يوجد طبقة واحدة من الخلايا مسطحة، وقارن هذا ب表층 متعدد الطبقات، حيث يمكن أن تختلف شكل الخلايا في الطبقات الأعلى.

Q & A

ما هي الأنسجة البيئية؟

الأنسجة البيئية،とも称为 epithelium،هي مجموعة من الخلايا المتماسكة ببعضها البعض،تغطي أطراف الجسم أو مساحات داخلية.

ما هي الأنواع الرئيسية للأنسجة البيئية؟

هناك نوعان رئيسيان للأنسجة البيئية: التغطية والشطف،تغطي الأطراف الخارجية من الجسم مثل الجلد أو تشطف مساحات داخلية مثل المسار التنفسي أو القناة الهضمية.

ما هي الوظيفة الرئيسية للأنسجة البيئية؟

وظائف الأنسجة البيئية تشمل الحماية، ال吸引力، التصفية، الإخراج، والسرية، وكذلك الكشف الحسي.

ما هي الخصائص الخمس التي تميز الأنسجة البيئية؟

الأنسجة البيئية تتميز بوجود polarity،specialized contacts،دعم من الأنسجة ال結蹄،عدم وجود دم في الداخل،وأن تكون innervated.

لماذا تعتبر الأنسجة البيئية 'لا تحتوي على دم'؟

تسمى الأنسجة البيئية 'لا تحتوي على دم' لأنها لا تتضمن أنسج دموية داخلها،ولذلك تعتمد على الأنسجة ال結蹄 الأساسية لتقديم الدعم اللازم.

ما هي الوظيفة الرئيسية للشبكة القاعدية؟

الشبكة القاعدية تساعد في تعزيز ودعم ورقة الخلايا البيئية،تمنع الامتداد والشق،وتحدد حدود الأنسجة البيئية.

لماذا تتطلب الأنسجة البيئية قدرة استئنافية عالية؟

تتطلب الأنسجة البيئية قدرة استئنافية عالية لأنها تتعرض لعوامل تضررية وتحتاج إلى استبدال دائم.

ما هي التصنيفات الرئيسية للأنسجة البيئية؟

تصنف الأنسجة البيئية بناءً على عدد طبقات الخلايا وشكل الخلايا،مثل ال组织的简单 o stratified،和平 squamous cuboidal columnar.

ما هي الفرق بين epithelium بسيط و متعدد الطبقات؟

ال组织的简单 epithelium يحتوي على طبقة واحدة من الخلايا،بينما يحتوي epithelium متعدد الطبقات على طبقات متعددة.

كيف يتم تسمية الأنسجة البيئية متعدد الطبقات؟

يتم تسمية epithelium متعدد الطبقات بناءً على شكل الخلايا في السطح الأعلى لل上皮，مثل stratified squamous.

ما هي العوامل التي تؤثر على شكل الخلايا في epithelium متعدد الطبقات؟

الشكل الخلية في epithelium متعدد الطبقات يختلف بناءً على الموقع،مثل الsquamous في السطح الأعلى،والcuboidea والcolumnar في الطبقات السفلى.

Outlines

00:00

🔬 Epithelial Tissue Structure and Function

This paragraph introduces the concept of epithelial tissue, also known as epithelium, which is a tightly bound sheet of cells that cover body surfaces or line cavities. It distinguishes between two major forms: covering and lining epithelia, with examples such as skin and the lining of the respiratory or digestive tract. Glandular epithelia are also mentioned, which line the ducts of glands like the salivary glands or pancreas. The paragraph highlights the main functions of epithelial tissues, including protection, absorption, filtration, excretion, secretion, and sensory reception. It also outlines five key characteristics of epithelial tissues: polarity, specialized contacts, support by connective tissue due to their avascular nature, innervation, and a high regenerative capacity due to their exposure to damaging factors.

05:03

📚 Classification of Epithelial Tissues

The second paragraph delves into the classification of epithelial tissues, which is based on the number of cell layers and the shape of the cells. Simple epithelial tissues consist of a single layer of cells, while stratified epithelial tissues have two or more layers, such as the skin. The shape of the cells is described with terms like squamous (flattened), cuboidal (cube-like), and columnar (taller than wide). The classification is further explained by using examples of simple and stratified epithelia, emphasizing how the shape of cells at the apical surface determines the type of stratified epithelium. The paragraph also discusses the importance of understanding three-dimensional cell structures when examining them under a microscope, as they may appear different in two-dimensional views.

Highlights

Epithelial tissue, also known as epithelium, is a tightly bound sheet of cells that cover body surfaces or line cavities.

There are two major forms of epithelial tissues: covering and lining epithelia.

Glandular epithelia line the ducts of glands and are involved in secretion.

Epithelial tissues perform functions such as protection, absorption, filtration, excretion, secretion, and sensory reception.

Epithelial tissues have five distinguishing characteristics: polarity, specialized contacts, support by connective tissue, innervation, and high regenerative capacity.

Epithelial tissues are avascular, lacking blood vessels, and are supported by underlying connective tissue for nourishment.

Epithelial tissues are innervated, containing nerve supply for sensory reception.

High regenerative capacity is necessary for epithelial tissues due to exposure to damaging factors.

Polarity in epithelial tissues refers to the distinct apical and basal surfaces with different structures and functions.

The apical surface is involved in secretion, protection, and absorption, while the basal surface is involved in attachment and transportation.

Epithelial tissues have specialized contacts such as tight junctions for waterproofing and desmosomes for strong cell adhesion.

The basement membrane, composed of basal and reticular laminas, reinforces the epithelial sheet and resists stretching.

Connective tissue supports epithelial tissues by providing nutrients through diffusion due to the absence of blood vessels.

Epithelial tissues are classified based on the number of cell layers (simple or stratified) and the shape of the cells (squamous, cuboidal, columnar).

Stratified epithelia can have varying cell shapes in each layer, classified by the shape of cells at the apical surface.

Examples of simple epithelium include the alveoli in the respiratory tract for rapid gas absorption.

Stratified squamous epithelium, like in the skin, is an example of a multi-layered tissue with flattened cells at the surface.

Microscopy images of epithelial tissues show two-dimensional views of three-dimensional structures.

Transcripts

okay in this video we're going to talk

about the epithelial tissue so

epithelial tissue also called epithelium

is basically a sheet of cells that are

all tightly bound together

and these cover body surfaces or

cavities there's two major forms we have

covering and lining epithelia that you

find let's say

you know covering your whole body like

skin or lining the internal surfaces of

your body like

all on your respiratory tract or all

along the inside of your digestive tract

these would form the walls

of those spaces now the glandular

epithelia

are involved with lining the the

ducts of a gland things like salivary

glands or pancreas

have epithelial tissues that line those

ducts and they even

make part of this secretion that we'll

talk about here in a minute

some of the major functions of

epithelial tissues are to protect

absorb to filter to excrete

an excretion is elimination of wastes to

secrete

you know saliva obvious secretion and

some epithelia are involved with sensory

reception so they're used to pick up

information in your body

now the epithelial tissues of our body

have five distinguishing characteristics

we say they have polarity

specialized contacts they're supported

by connective tissue

and this is because epithelial tissues

are avascular so a meaning lacking

vascular means blood

blood vessels so avascular means that

epithelial tissues do not have blood

vessels within them

this is why they're supported by an

underlying connective tissue

that's because the connective tissues

can bring in the blood vessels and

nutrients that can

basically nourish those epithelia but

epithelial tissues are

innervated which means they get nerve

supply so that you do find nerves within

epithelial tissues

also epithelial tissues need have a high

regenerative capacity

um this is because they're involved with

protection and

uh they're you know exposed to a lot of

damaging factors so they need to be able

to regenerate pretty frequently

so polarity refers to the fact that

epithelial tissues have a top and a

bottom

the top is what we refer to the apical

surface surface now the apical surface

is this

upper free side or you can also call

this the side that's exposed to your

surface or cavity

so an example of where you'd find this

would be if you look at your skin

the side of the cells you're looking at

when you're viewing your skin

externally is the apical surface of

those epithelial cells

and then deeper those epithelial cells

would be attached by their basal surface

to an underlying basal lamina of

basement membrane

and then that would be attached to an

underlying connective tissue

now both surfaces differ in their

structure and function because the

apical surface is involved with

secretion and protection and absorption

whereas the basal surface is involved

with attachment

and also transportation of certain

materials

epithelial tissues need to have lots of

specialized contacts

so going back to when we talk about the

intercellular junctions of chapter three

we said we had tight junctions and

desmosomes remember tight junctions were

involved with waterproofing so that

water can't pass between cells

and desmosomes were involved with very

strongly holding cells together

so we find that epithelial tissues have

a lot of these because we really need

those

cells to be tightly bound together and

not pass

substances between them now connective

tissues all

support epithelial tissues and

what we find is that the epithelial

sheets are basically these long mats of

cells that are all interconnected

are supported by an underlying

connective tissue at some point

now uh we have this reticular lamina

that's deep to the basal lamina and it's

basically a network of collagen fibers

that

these epithelial cells attach to this is

part of the basement membrane so the

basement membrane is made of the basal

and reticular laminas

it's basically something that reinforces

the epithelial sheet

think of this as like the velcro for the

cells to attach to

this base membrane also resists

stretching and tearing and it defines

the epithelial boundary

because just deep to basement membrane

that's when you have the underlying

connective tissue

that would basically help to support and

nourish the epithelium

now we need an underlying connective

tissue because epithelial tissues are

avascular

which means that they don't have blood

vessels within them but they do have a

lot of nerve supply

so because of the fact that epithelial

tissues don't have blood vessels within

them

they need to be nourished by diffusion

or you know sort of

movement of particles from an underlying

connective tissue

now these epithelial do have nerve

fibers and these are involved with

receiving information in different areas

of your body

now epithelial tissues also have a high

regenerative capacity

this is because they are exposed to

friction

or hostile substances which can result

in damage

and therefore must be replaced and it

requires an adequate amount of nutrients

as well as cell division to adequately

replace those epithelia

what something else that stimulates the

regeneration of epithelial tissues is

this

loss of apical basal polarity or broken

lateral contacts that way the tissue

knows that

um you know there are spaces that need

to be filled in

with new cells now what we'll do next is

move on and talk about the

classification of epithelial tissues

so all epithelial tissues have two names

the first part of the name

indicates the number of cell layers so

if we say it's a simple epithelial

tissue it means it has a single layer of

cells

if it's a stratified epithelial tissue

it has two or more cell layers thick

an example this would be skin where you

have you know probably over

30 cell layers thick so we would call a

stratified epithelium

you'd find an example of simple

epithelium like in your respiratory path

uh passages specifically the alveoli

where you need to absorb rapid

absorption of gases

now another name here would indicate the

shape of the cells

so squamous means that the cells look

kind of flattened or scale like

cuboidal means they look box like like a

cube and columnar means they're taller

than they are

wide or column like so we do that is we

can mix

these the combinations of these words

here so we can have simple

squamous epithelium or stratified

cuboidal epithelium

and that tells you basically the number

of cells and the shape of those cells

in the stratified epithelia the shape

can vary in each layer so

ultimately we classify the stratified

epithelium

based on the shape of the cells at the

apical surface

of the epithelium and i'll give you guys

an example here in a minute

so you can see here is a classic example

of simple squamous epithelium

we can tell it's simple squamous because

you have one layer of cells here

and they're flattened which means

they're squamous so we said it's a

simple squamous

now we can compare this down here to a

stratified epithelium

and if you look first of all you can

tell this is stratified because you have

many cell layers that are stacked

upon each other now you might wonder

okay well these cell shapes can kind of

vary the closer you get to the surface

and you might say okay these ones kind

of look cube shape so then you might be

inclined to say stratified cube oil

where you have

you know many layers of cube shaped

cells however the stratified epithelial

tissues

uh that are named for the shape of the

cells

at the apical surface you can see that

apically we see that these cells are

more flattened

so we would call this type of epithelium

actually stratified squamous which is

basically like what you'd find in your

skin

now remember squamous is flattened

cuboid is cube shaped and columnar is

more column shaped

you'll find that when you look in a

microscope

they're not going to be in their

three-dimensional views they're going to

see more two-dimensional like this

so we start looking at microscopy images

here pretty soon

you'll see cells that are shaped like

this we see there's squamous or

cube shaped cuboidal or columnar down

here which are more column shaped

but in reality they're actually

three-dimensional structures here