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Unit 2 Histology and Embryology
Key to the Exercises
1. Preparation
Enjoy a video clip. You may watch it twice to achieve a good understanding. After watching, please answer the following questions.
1) The skin.
2) Epidermis.
3) Keratin.
4) The times of the images being magnified by the microscope.
Script
Look, a bare hand. We sometimes lay our forehead on it when we feel tired. The
envelope of the body, a living border between the inside and the outside, between the wet
and the dry, the skin is an assembly of regular cells. It's covered with a network of
furrows and plateaus. The translucent spheres are drops of sweat which have reached the
surface through pores. The skin thus evolves, breathes and perspires, getting rid of
certain wastes of the body. This tormented landscape is our epidermis, magnified 150
times within it the layers of cells are in constant renewal. Cells are already dead when
they reach the surface, disposed of and replaced by others produced in deeper layers.
Here is a hair, magnified 180 times its root, invisible on the screen, loses itself in the
epidermis. A slight cut, this gray area at the center of the image, allows us to distinguish
the various cell layers that constitute the epidermis. As we move deeper, we come across
living cells whose nucleus we can sometimes distinguish, those regular bubbles we can
see at the bottom of the screen. Above, flat cells, emptied of their content ! constitute the
upper layer of the epidermis. Within these, we find a very resistant protein, keratin ·
which can also be found in hair, and nails, and teeth. Here we are now at the heart of the
epidermis. The membranes form a protective waterproof barrier. For this very purpose,
they are joined together by something like a press stud, this dark crescent at the center
of the image. Yet we can also see how they are arranged in lipid layers placed side by
side1limiting exchanges with the outside. our microscope has unfortunately now reached
its limits. Beyond this, nothing more is visible for the moment.
ll. Reading
Comprehension Check
Pair work Discuss and answer the following questions. Try not to look back at the text.
1) The largest organ of the body is the integument, which is composed of skin and skin
appendages--nails, hair, sweat glands, and sebaceous glands. (Para. 1 )
2) Skin serves as a protective barrier against injury ( e. g., abrasions, cuts, burns),
infectious pathogens, and ultraviolet radiation, and assists in body temperature
regulation, vitamin D synthesis, ion excretion, and sensory reception (touch and pain).
(Para. 1 )
3) Four or five. In a deep to superficial direction, they are the stratum basale ( or
germinativum). The stratum spinosum, the stratum granulosum, the stratum lucidum
(absent in thin skin but present in thick skin) rand the stratum corneum. (Para. 2)
4) Blood vessels in the dermis and eccrine sweat glands can regulate temperature. (Para.
3 &. 5)
5) Apocrine sweat glands are less coiled than eccrine sweat glands, and the lumen of the
secretory tubules in the former has a wider diameter and larger, more numerous
myoepithelial cells than that in the latter. (Para. 6)
6) The cells of both parts contain keratin ; however, the most superficial cells of the
stratum corneum desquamate while the cells of nail plates do not. (Para. 2 & 9)
Language Practice
1. Read the text carefully and then fill out the missing information in the following short
passage. The beginning letter of each missing word has been given.
1) integumentary 2) regulating 3) epidermis
4) stratum 5) keratin 6) corneum
7) shed 8) dermis 9) vessels
10) subcutaneous 1 1) sweat 12) sebaceous
13) sebum 14) follicle
2. Paraphrase the following sentences. Pay special attention to the underlined parts.
1) Four or five layers, which are clearly different from one another, make up the
epidermis.
2) The next layer is the stratum spinosum. It is several cells thick and has polyhedral
cells that steadily and continuously become flatter toward the surface.
3) A fixation artifact decreases the size of the cell. This condition makes the projecting
parts on the cell surface more prominent, and these prominent parts become spines
or prickles. For this reason, we call them prickle cells.
4) Nerve fibers covered by a myelin sheath provide nerve endings to the epidermis and
sensory receptors enclosed in a capsule in the dermis...
5) The surface under the uncovered and hidden parts of the nail plate is the nail bed.
3. Identify the expression from each of the following sentences which corresponds in
meaning to one of the Chinese expressions given below. (These sentences are well written.
It is suggested that you read them aloud and learn them by heart. )
1)vary regionally因部位(不同)而异
2)serve as作为
barrier against抵御······的屏障
assist in协助参与
3)attach...To将······附在······上
4) (be) parallel to 与 · · · · · · 平行
5)(be) absent in在······中缺如不存在于······中
(be)present in出现于
6) (be) involved in 参与
7)in response to对······应答对······有反应
8)(be)lined by由······衬里(覆盖内表面)
9) (be) oblique to 与 · · · · · · 成斜角
4. Translate the following sentences into English with some expressions you have identified
in exercise 3.
1) osteoclasts are involved in the breakdown of bone tissue to release minerals needed
by the body or to allow for reshaping and repair.
2) The membranes of the smooth endoplasmic reticulum serve as surfaces for the
attachment of many enzyme systems.
3) An increase in the number of reticulocytes indicates increased red blood cell
formation, as in response to hemorrhage or destruction of red blood cells.
4) The acrosome covers half of the nuclear surface and contains enzymes to assist in
penetration of the egg during fertilization.
5) Sometimes chromosomes break, and pieces of one chromosome attach to those of
another.
6) The most superficial layer consists of densely packed fibers of type 1 collagen that
are arran9ecl almost parallel to the articular surface.
7) Follicles generally atrophy with increasing age and may be absent in the very
elderly.
8) The inner surface of the bone is lined by a thinner, more cellular endosteum.
9) Hematopoietic stem cells present in the liver are in greater numbers before birth
than afterward,
1o) This type of epithelium is a barrier against different types of injury, microbial
invasion and water loss.
11 ) Where fibers are oblique to the line of pull, muscles may be triangular or pennate.
12) Differentiation of transplanted neural precursors varies regionally in adults'
striatum.
Text B
comprehension Check
Answer the following questions. Try not to look back at the text.
1 ) It means a fertilized oocyte, a highly specialized, totipotent cell. (Para. 1 )
2) Differentiation and growth of tissues and organs occur during the fetal period. (Para. 2)
3) Prenatal development of embryos and fetuses is generally covered by the study of
embryology. (Para. 2)
4) What can help the parents not to put blame on themselves is the explanation of the
developmental basis of abnormalities by health care providers who understand the
common congenital anomalies and their causes. (Para. 11 )
5) People are concerned about the social, ethical, and legal implications of human cloning and
the possibility that cloning may result in birth defects and serious diseases. (Para. 13)
6) They are used to refer to the relationships to the head and caudal eminence ( tail ),
respectively. (Para. 15 )
Language Practice
Translate the following sentences into English. You are required to use the phrase (s) after
each Chinese sentence in constructing the corresponding English sentence.
1 ) Bacterial cells that express one phenotype can be transformed into cells that express a
different phenotype.
2) Developmental anatomy is the field of embryology concerned with the changes that
cells, tissues, organs, and the body as a whole undergo from a germ cell of each parent
to the resulting adult.
3 ) Embryology bridges the gap between prenatal development and obstetrics.
4) Embryology is of practical value in helping understand the causes of variations in
human structure.
5) Regulation of cell numbers is essential for maintaining proper physiological balance
among the various tissues and cell types.
6) These techniques are now widely used in research laboratories to address such diverse
problems as the genetic regulation of morphogenesis : the temporal and regional
expression of specific genes, and how cells are committed to form the various parts of
Human embryonic stem ( hES ) cells hold great potential for cell therapy and
7) regenerative medicine because of their pluripotency and capacity for self-renewal.
III. Video Watching and Speaking
Clip One
please Joltow tite video clip to take (I close look at the human skin land do the exercises
below.
1. Complete the following chart to illustrate the basic structure of the skin.
stratum corneum
epidermis)
basal layer
thermal receptors
Skin< Meissner's corpuscles
dermis free nerve endings
sweat glands, hair follicles and blood vessels
2. Match the following items with their corresponding functions.
1 ) D) 2) C) 3)A) 4 ) B)
3. Omitted.
Script
The body's largest organ-the skin-serves as a protective coat, guarding I
structures from the outside environment. It is composed of two distinct layers of
the epidermis and the dermis. The epidermis consists of an outer sheet of deal
called the stratum corneum, and a deeper section of rapidly dividing cells, called the basal
layer. When dead cells of the stratum corneum were damaged or scraped off during body
activity, cells from the basal layer rise to replace them. The epidermis serves as the
body's initial barrier to invading foreign substances. Directly below the basal layer is the
thicker dermis layer, made of dense connective tissue. Embedded within the dermis are
several kinds of important sensory receptors, including thermal receptors, which detect
temperature change, Meissner's corpuscles which are sensitive to touch, and free nerve
endings which detect pain and tissue damage. The dermis also contains many other
structures, including sweat glands, hair follicles and blood vessels.
Clip Two
Watch the video clip and do the exercises below.
1. Multiple choice.
1 ) B 2)D 3)B 4 ) C 5)D
2. Fill in the blanks in the following paragraph.
1) attaches 2) placenta 3) intermingles
4) nutrients 5) rejected 6) organism
7) genetic 8) abdomen 9) belly button
10) pregnancy 11 ) intense 12) doubles
13) 21 14) kicks 15) beats
Script
As the cells divide, the embryo continues its journey along the fallopian tube. About
one week after conception, it reaches the uterus which is prepared to receive it with the
network of blood vessels and glands. By this time, the embryo has become a fluid-filled
sphere of nearly one hundred cells. Some of the cells become finger-like projections that
anchor the embryo to the uterus to draw nourishment and oxygen and to rid the embryo
of wastes. The anchoring cells secrete a hormone that will prevent the disintegration of
the lining. There will be no menstrual period. Three weeks after fertilization, though
still smaller than a grain of rice, the embryo has a primitive heart. Through the
following weeks, its tissues and organs will develop. In four weeks, it looks like this.
Five weeks, about the size of a pea. Six weeks. Seven weeks. At two months, it is called
a fetus and is obviously human, though only the size of a gumdrop. When the embryo
attaches to the uterus, a complex structure of vessels and cells forms, which is called the
placenta. A network of the embryo's blood vessels closely intermingles next to the
mother's blood supply. While their blood doesn't actually mix. Materials such as
oxygen, nutrients and waste products can pass between mother and child. If their blood
were to mix, the embryo would be rejected as the foreign organism that, in fact. It is.
Don't forget it shares only half of its genetic constitution with its mother. From the
placenta emerges the umbilical cord which leads to the abdomen of the fetus. When the
cord is removed at birth, the belly button is created. During pregnancy, the placenta and
umbilical cord serve as pathways for everything the fetus needs to grow. By the third
month. All the organs of the fetus are essentially in place and it enters the period of
intense growth. During the fourth month, the fetus doubles in size. Its muscles twitch,
By the fifth month, it is nearly 21 cm long, about 9 inches. It kicks occasionally. Its heart
beats about 14o times per minute, twice the speed of an adult.
IV. Writing
Improve the following sentences : putting the action in the verb. The underlining may serve
you as a clue.
1 ) At the basal surface, hemidesmosomes aid in attaching the cells to the underlying
basement membrane.
2) Fibrillinmicrofibrils attach the lamina densa to elastic fibers.
3) The rod shaped granules fuse with the plasmalemma.
4) A deficiency of melanin may also occur.
5) When eccrine sweat glands are involved in emotional sweating, they are controlled by
postganglionic sympathetic neurons that release norepinephrine.
V. Autonomous learning
Vocabulary Development
1. Fill in each of the following blanks with an appropriate word.
1 ) tissues 2) forms 3) nucleus 4) ingestion
5) attracting 6) fat 7) skin 8) melanin
9) keratin 10) fetus
2. Match each of the following terms with its meaning and write the appropriate letter to the
left of each number.
Group 1 1 ) d 2) e 3) a 4) b 5) c
Group2 6) j 7) I 8)f 9) g 10) h
3. Give the meaning for each of the following terms.
1 ) before operation
2) above the stomach
3) across the abdomen
4) a poor condition of health caused by a lack of food
5) visible with the naked eye
Supplementary Listening
script
A woman's reproductive cell is commonly called an "egg", but the correct term
"oocyte". Likewise, a man's reproductive cell is widely known as a "sperm", but the
preferred term is "spermatozoon". Following the release of an oocyte from a woman
ovary in a process called ovulation, the oocyte and spermatozoon join within one of the
uterine tubes which are often referred to as fallopian tubes. The uterine tubes link a
woman's ovaries to her uterus or womb. The resulting single-celled embryo is called a
zygote, meaning "yoked or joined together". The zygote's 46 chromosomes represent the
unique first edition of a new individual’s complete genetic blueprint. This master plan
resides in tightly coiled molecules called DNA. They contain the instructions for the
development of the entire body.
