细胞、组织的适应在线视频

大家好 今天我来给大家讲细胞和组织的适应

那么 什么叫做适应性反应呢

机体在外界环境改变的条件下 为了避免发生损伤 会发生代谢以及功能和结构方面的改变

这个改变的过程 我们就称之为适应

适应主要分为四大类 萎缩 肥大 增生和化生

萎缩 肥大 增生主要指细胞在体积和数量上的改变

而化生主要指在细胞的类型上的改变

我们来具体看一下

首先来介绍萎缩

萎缩的概念指的是发育正常的器官和组织的实质细胞体积变小 数量减少 最后导致器官或者是组织体积的缩小

发育正常 这是一个要点

那么我们过去学过的 未发育的 或者是发育不全的脏器 体积也很小 但这种不能够做萎缩

根据萎缩的原因不同 可以分为生理性和病理性萎缩两大类

病理性萎缩又可以具体根据病因的不同 分为营养不良性萎缩 神经性萎缩 失用性萎缩 压迫性萎缩 内分泌性萎缩以及缺血性萎缩六大类

接下来我们来详细看一下

对于一个萎缩的组织或者是器官

从肉眼上观察 体积会减小 相应的质量也会减轻 颜色变深

这种改变的基础是由于 从光学显微镜下观察到的每一个实质细胞的体积都会变小 数量都会减少

与之相对应相反的是 体积和数量的减少指的是实质细胞的改变

而相对应的间质纤维组织却发生增生 间质里边的脂肪组织会增多

同时，在胞浆里边偶尔会见到一种特殊的色素颗粒的沉积 叫做脂褐素

后续我们会给大家详细介绍

根据病因的不同 刚才说过可以分为生理性萎缩和病理性萎缩两大类

生理性萎缩，顾名思义 是生命过程中的一个正常现象

举几个例子 比如在青春期 胸腺会发生萎缩 这个叫做退化

成人期在女性分娩之后的子宫以及哺乳期后的乳腺恢复正常的体积 这个也叫生理性萎缩

我们称之为复旧

还有一种是老年人的脏器和组织随着年龄的增加 逐渐体积变小 这种叫做老年性萎缩

这些都是正常现象 所以叫做生理性萎缩

与之对应的另外一种 叫做营养不良性萎缩

营养不良性萎缩见于长期饥饿或者是肿瘤晚期的一种恶病质状态

在这种情况下 比如食道癌的患者

食道吞咽困难 长期的疼痛 会导致营养不良 导致全身各个脏器的萎缩

第二种叫做失用性萎缩

比如骨折的患者长期卧床不能够活动

那么骨骼肌就会体积减小 肢体变细 这叫失用性萎缩

也叫用进废退 是一个道理

第三个分类叫做神经性萎缩

因为正常的骨骼肌肌肉是需要神经末梢进行支持和营养的 对他进行调节

比如在一种疾病 叫做脊髓灰质炎

患者的脊髓前脚运动神经元受损 它所支配的神经末梢所控制的这一部分骨骼肌 就会相应的发生萎缩变细

神经性萎缩 是由于神经受损所导致的肌肉的萎缩

第四种叫做压迫性萎缩

是过高的压力导致各组织脏器的实质部分发生萎缩

举个例子 比如尿路结石

大家现在看到的这个图片是一个肾盂积水的一个病例

我们可以看到 整个肾脏的实质内 由于尿路的结石导致原尿尿液无法排出 积聚在肾盂和肾盏内

积聚的尿液压力增高 就会引起肾实质的萎缩变薄

这个是肾盂积水，也叫做压迫性萎缩

第五大类叫做神经内分泌性萎缩

神经内分泌性萎缩主要是由于一些神经内分泌的器官的功能低下所导致的相应的靶器官体积的减小

比如Sheehan病 是一种垂体的功能的低下 比如产后大出血导致的垂体功能低下

那么垂体下游的靶器官 比如性腺 肾上腺 甲状腺都会发生相应的萎缩

第六大类叫做缺血性萎缩

我们看一下这幅图片

这是脑组织

脑血管在发生缺血的时候 比如动脉粥样硬化时

所供给的这一部分脑实质就会发生萎缩

我们可以看到脑沟变得很深 脑回变窄

除了脑组织 心脏也是一样

冠状动脉粥样硬化 供血不足的时候 就会发生相应冠脉所供给的心肌发生萎缩

这是六大类的病理性萎缩

接下来我们看一下这幅图片 可以看到横纹肌的肌纤维明显的变细

在横纹肌之间 在发生萎缩的时候 间质会浸润到横纹肌的肌束之间

这是一个萎缩的现象

我们在这幅图片下面看到的是正常的心肌的结构由横纹肌所构成

那么在萎缩发生的时候横纹肌的肌纤维也是明显的变细 细胞的体积明显的缩小 胞浆染色变淡

这是萎缩的改变

我们接下来再看这张图片

我们刚才提到了 在发生萎缩的时候

细胞的胞浆里面会出现脂褐素的沉积

所以在这幅图片里 心肌细胞两侧的胞浆里面都看到了棕黄色颗粒

这是一种脂褐素颗粒的沉积

当引起萎缩的这种原因被去除以后 是可以恢复到原有的正常大小的

但是如果这种致病原因继续发展的话 萎缩的细胞最后是可以逐渐消失的

那么整体来看 萎缩最后他的器官体积会变小 质地会变硬

相应的 功能也会低下

The second category is called hypertrophy

Hypertrophy refers to an increase in the size of tissue or organs

Why does the volume increase?

It mainly due to increase amount of cytoplasmic organells which makes the volume of tissue or organ increase uniformly

More nutrition and oxygen are needed in order to adapt the change of environment

Similarly hypertrophy can also be divided according to the cause as physiological hypertrophy and pathological hypertrophy

First is physiological hypertrophy

For example the volume of the uterus during pregnancy will increase

It shows in this slide

The relatively smaller uterus is of normal size while during pregnancy its volume can obviously increase which belongs to physiological hypertrophy

Next this is the normal morphology of uterine striated muscle fiber

During pregnancy the muscle fiber became thick and cytoplasm increased

On the other hand there is pathological hypertrophy

Pathological hypertrophy can be classified as two categories including compensatory hypertrophy and endocrine hypertrophy

What is compensatory hypertrophy?

This is due to the increasing workload of certain tissue or organ

For example hypertrophy of ventricular wall occurs in patient with hypertension

The higher pressure requests more workload of myocardium thus needs more systolic activity eventually results in myocardial hypertrophy

There is another example

When one of the kidney was removed for treatment purpose the other one shall compensate the loss of function

Therefore there are more units of nephrons from the residual kidney becoming functional accompanied by the increased renal function

The second category is called endocrine hypertrophy

It is due to the hyperplasia or tumor of endocrine organ

Excessive secretion of hormones cause organ hypertrophy

Let's take a look at this compensatory hypertrophy of heart

This is a normal microscopic view of myocardium

We can see that each individual cells underwent hypertrophy with pink stained and abundant cytoplasm

On the gross view the thickness of the myocardial wall including interventricular septum became thickening obviously

That is because of the size increase of each individual cells

The third category is called hyperplasia

Hyperplasia constitude an increase in the number of cell

Similar to hypertrophy increase in numbers of parenchymal cells can also result in volume increase of the tissue or organ

Actually increase of size of the tissue is due to combination of hypertrophy and hyperplasia

For exampleas we have just learned that

the volume increase of uterus during pregnancy not only associates with increased cell volume but also number of the cells

These hormone-related hyperplasia can be seen in uterine smooth muscle cell during pregnancy and breast ductal epithelial cell during lactating peroid

These are both hormone-induced physiological hyperplasia

There is another type called compensatory hyperplasia

For example after partial hepatectomy

The liver will grow back to its original cell number and volume by the remaining stem cells after certain period of time

This is called compensatory proliferation

Pathological hyperplasia can be devided into endocrine hyperplasia and inflammatory repair hyperplasia

For example excessive secretion of estrogen may cause endometrial hyperplasia and breast hyperplasia

These are very common diseases

Excessive androgen secretion may cause prostate hyperplasia

The other type is inflammatory repair hyperplasia which we are going to learn later

When inflammatory occurs various cells like fibroblast and endothelial cells will fix the injured tissue

Then the original structure and function are able to be restored

This also belongs to pathological hyperplasia

This slide shows an inflammatory repair hyperplasia

There is normal gastric epithelium at both sides

This polypoid protrution here is the gastric inflammatory repair polyp

This is also known as proliferative polyp

On the high power view there are increased number of glandular structure and epithelial hyperplasia as well

The last category of adaptation is called metaplasia

It refers to a process in which one matured tissue type is replaced by another matured tissue type

In this process the transformation goes only between tissues with similar properties

It means metaplasia occurs between epithelial tissue or between mesenchymal tissues

Metaplasia does not occur between epithelial and mesenchymal tissues

This is the first key point we shall remember

Then the second key point is

during the process of metaplasia

The metaplastic cells are not coming from mature cells

Instead metaplasia results from the differetiation of undifferented cells or stem cells

This picture below shows columnar epithelium

Normally there are some reserve cells at the base part of columnar epithelium which is called stem cells

Stem cells have the potential to divide and differentiate

Mature squamous epithelium are actually differentiated from reserve cells

It's not coming from the mature columnar epithelium

There are several common types of metaplasia

The first type is important and is called epithelium metaplasia

Bronchial columnar epithelium may turn into squamous epithelium after a long-term stimuli of chronic inflammation in patient such as heavy smoker

It's very important because the squamous metaplasia is a sort of precancerous lesion of squamous cell carcinoma of bronchus

We take chronic cervicitis as another example

Columnar epithelium on cervix may undergo squamous metaplasia

which is also the precancerous lesion of cervical squamous cell carcinoma

Let's first take a look at the bronchial squamous cell metaplasia

Under normal circumstances the bronchial mucosa is covered by pseudostratified columnar epithelium

However entirely replaced by squamous epithelium under the microscopic view

which is called squamous metaplasia

This slide shows the squamous metaplasia of cervical mucosa

The normal columnar epithelium has been replaced by squamous epithelium

The second category is intestinal metaplasia

which happens on cases with chronic atrophic gastritis or gastric ulcer

Epithelium of gastric mucosa is replaced by small intestinal or colorectal like mucosa

It's believed to be the precancerous lesion of intestinal type gastric cancer especially for the colorectal epithelial metaplasia

Under the microscopic view

We can find here the gastric mucosa

Meantime we see a lot of goblet cells

which is the characteristic feature of intestinal epithelium

So we say this is intestinal metaplasia

The second category happens between mesenchymal tissues

which means one kind of mesenchymal tissue turns into another

For example fibroblasts can turn into osteoblasts or chondroblast

Then turns into bone or cartilage tissue

This slide shows the myositis ossificans

Just as the term tells us that myositis ossificans occurs when there is tissue injury

bone tissue forms inside muscle or other connective fibrous tissue

As we can see that there are formation of trabecular bone tissue

This is the mataplasia between mesenchymal tissue

Muscle turn into connective tissue with the calcium deposition bone tissue gradually formed

Here is the summary of the adaptation

There are four kinds of adaptation for a normal cell

Atrophy refers to a decrease in the volume or number of cells

Hypertrophy refers to an increase of cell size

Hyperplasia refers to the increase of number of cells

Metaplasia is different from those

Metaplasia is the change of cell type without affecting the number or volume of cells

That's all for today