Intro to HA and Embryology

Question 1

Sagittal,
coronal and
transverse
planes

Answer 1

Sagittal Plane: Divides the body into left and right portions (midsagittal if equal, parasagittal if unequal).
Coronal Plane (Frontal Plane): Divides the body into front (anterior) and back (posterior) parts.
Transverse Plane (Axial Plane): Divides the body into upper (superior) and lower (inferior) sections horizontally

Question 2

Foetus/embryo

Answer 2

Embryo: Refers to the early stage of development after fertilization, typically from conception until the 8th week of pregnancy. During this period, the basic structures and organs of the body begin to form.

Foetus: Refers to the later stage of development, starting from the 9th week of pregnancy until birth. During this time, the structures formed during the embryonic stage continue to develop and mature.

Question 3

Dorsal

Answer 3

Dorsal: Refers to the back or upper side of an organism. In humans, it generally indicates the back (posterior side), while in animals (like quadrupeds), it refers to the upper side or the side facing the sky

Question 4

Ventral

Answer 4

Ventral: Refers to the front or belly side of an organism. In humans, it indicates the anterior or front side of the body. In animals, particularly quadrupeds, it refers to the lower side or the side facing the ground.

Question 5

Notochord

Answer 5

The notochord is a flexible, rod-like structure that forms in the early development of all vertebrates, including humans. It serves as the primary support structure during the embryonic stage and plays a crucial role in the development of the vertebral column (spine). In most vertebrates, the notochord is eventually replaced by the vertebrae as the embryo matures, though remnants of it can persist in the intervertebral discs.

Question 6

Medial

Answer 6

Medial: Refers to a position closer to the midline of the body, which divides the body into equal left and right halves. For example, the nose is medial to the eyes because it is nearer to the body’s midline

Question 7

Lateral

Answer 7

Lateral: Refers to a position further from the midline of the body, or towards the sides. For example, the ears are lateral to the eyes.

Question 8

Body Cavities

Answer 8

The human body contains several body cavities, which house and protect internal organs. The two main cavities are:

Dorsal Body Cavity:

Cranial Cavity: Contains the brain.
Spinal (Vertebral) Cavity: Contains the spinal cord.
Ventral Body Cavity:

Thoracic Cavity: Contains the lungs and heart, protected by the rib cage.

Abdominopelvic Cavity:
Abdominal Cavity: Contains digestive organs like the stomach, liver, and intestines.
Pelvic Cavity: Contains the bladder, reproductive organs, and rectum

Question 9

Embryonic Disc

Answer 9

The embryonic disc is a flat, two-layered structure that forms during the early stages of embryonic development, around the second week after fertilization. It gives rise to the entire body of the developing organism.

It consists of two layers:
Epiblast (upper layer): Forms the future ectoderm, mesoderm, and endoderm.
Hypoblast (lower layer): Contributes to the formation of the yolk sac but not the embryo itself.
This disc is crucial for the formation of the three primary germ layers during gastrulation, which ultimately develop into all the tissues and organs of the body

Question 10

Morula

Answer 10

The morula is a solid ball of cells that forms about 3 to 4 days after fertilization, consisting of 16 to 32 cells known as blastomeres. It results from the cleavage of a zygote, where the fertilized egg divides multiple times without growing in size. The morula eventually develops into a blastocyst, which is a hollow structure that will implant into the uterine wall, marking a critical step in embryonic development.

Question 11

Blastocyst

Answer 11

The blastocyst is a stage of embryonic development that occurs approximately 5 to 6 days after fertilization.

It is characterized by a hollow structure containing an inner cell mass (ICM) and an outer layer of cells known as the trophoblast.
The inner cell mass will eventually develop into the embryo, while the trophoblast will form part of the placenta and facilitate implantation into the uterine wall.
The blastocyst stage is crucial for successful implantation and the establishment of pregnancy, as it allows for the exchange of nutrients and waste between the mother and the developing embryo

Question 12

Amnion, chorion,
allantoic membrane

Answer 12

Amnion:

A membrane that surrounds the developing embryo, forming the amniotic sac.
It contains amniotic fluid, which cushions the embryo, protects it from mechanical shocks, and provides a stable environment for development.

Chorion:

The outermost membrane that surrounds the embryo and the other extraembryonic membranes.
It plays a critical role in gas exchange and contributes to the formation of the placenta in mammals, facilitating nutrient and waste exchange between the mother and embryo.

Allantoic Membrane:

A membrane that forms from the yolk sac and is involved in the storage of waste products from the embryo.
In reptiles and birds, it also aids in gas exchange and contributes to the formation of blood vessels that connect to the chorion for nutrient and gas exchange. In mammals, it becomes part of the umbilical cord.
Together, these membranes support the developing embryo and are essential for its growth and development.

Question 13

Inner Cell Mass

Answer 13

The inner cell mass (ICM) is a cluster of cells located within the blastocyst, which forms approximately 5 to 6 days after fertilization.

It is crucial because it will eventually develop into the embryo itself, giving rise to all the tissues and organs of the body.
The ICM is surrounded by the trophoblast, which will form the placenta.
The ICM differentiates into two layers: the epiblast (which will form the embryo and some extraembryonic tissues) and the hypoblast (which contributes to the yolk sac).
The inner cell mass plays a vital role in early embryonic development and the establishment of pregnancy.

Question 14

Implantation

Answer 14

Implantation is the process by which a developing blastocyst attaches to and embeds itself into the lining of the uterus, typically occurring about 6 to 10 days after fertilization.

Key Points:
Process: The trophoblast, the outer layer of the blastocyst, secretes enzymes that help it penetrate the uterine lining, facilitating attachment and invasion into the endometrium (the uterine lining).
Nutrient Supply: Once implanted, the trophoblast develops into the placenta, which becomes essential for nutrient and waste exchange between the mother and the developing embryo.
Hormonal Changes: Implantation triggers hormonal changes in the mother, notably the production of human chorionic gonadotropin (hCG), which helps maintain the pregnancy and prevents menstruation.
Significance: Successful implantation is crucial for establishing a viable pregnancy; failure to implant properly can result in pregnancy loss.
Implantation is a vital step in early embryonic development, setting the stage for the growth and formation of the embryo and placenta.

Question 15

Gastrula

Answer 15

The gastrula is a stage of embryonic development that follows the blastula stage, occurring around the third week after fertilization. It is characterized by the formation of three distinct germ layers: ectoderm, mesoderm, and endoderm

Question 16

Proximal

Answer 16

Proximal: Refers to a position that is closer to the point of attachment or origin of a structure, typically used in relation to limbs. For example, the elbow is proximal to the wrist because it is closer to where the arm attaches to the body.

Question 17

Distal

Answer 17

Distal: Refers to a position that is further from the point of attachment or origin of a structure, especially in relation to limbs. For example, the fingers are distal to the wrist because they are further away from where the arm attaches to the body.

Question 18

Neurulation

Answer 18

Notochord establishes axis of the embryo
* Notochord is replaced by the vertebral
column
* Formation begins of spinal cord and brain
(neurulation)
* Neural plate to neural groove to neural
tube: pinched off into body

Question 19

Systems

Answer 19

The human body is organized into several interconnected body systems, each with specific functions that work together to maintain overall health and homeostasis. Here’s an overview of the major body systems:

Circulatory System:

Composed of the heart, blood vessels, and blood.
Responsible for transporting oxygen, nutrients, hormones, and waste products throughout the body.
Respiratory System:

Includes the lungs, trachea, and diaphragm.
Facilitates the exchange of oxygen and carbon dioxide between the body and the environment.
Digestive System:

Comprises the mouth, esophagus, stomach, intestines, liver, pancreas, and gallbladder.
Responsible for breaking down food, absorbing nutrients, and eliminating waste.
Nervous System:

Includes the brain, spinal cord, and nerves.
Controls body functions through electrical signals and coordinates responses to stimuli.
Musculoskeletal System:

Consists of bones, muscles, tendons, and ligaments.
Provides structure, support, and movement to the body.
Endocrine System:

Comprises glands that secrete hormones (e.g., thyroid, adrenal, pancreas).
Regulates various bodily functions such as growth, metabolism, and mood.
Immune System:

Includes lymph nodes, spleen, thymus, and white blood cells.
Defends the body against pathogens and foreign substances.
Integumentary System:

Composed of the skin, hair, nails, and associated glands.
Protects the body, regulates temperature, and provides sensory information.
Reproductive System:

Involves the male (testes, prostate) and female (ovaries, uterus) reproductive organs.
Responsible for producing gametes and facilitating reproduction.
Urinary System:

Comprises the kidneys, ureters, bladder, and urethra.
Responsible for filtering blood, removing waste, and regulating fluid balance.
Lymphatic System:

Includes lymph vessels, lymph nodes, and lymph fluid.
Plays a role in fluid balance, immune function, and fat absorption.
Each of these systems works in harmony to support the overall functioning of the body, ensuring that it can respond effectively to internal and external changes

Question 20

Germ Layers

Answer 20

The germ layers are the three primary layers of cells that form during embryonic development, specifically during a process called gastrulation. These layers give rise to all the tissues and organs in the body. The three germ layers are:

Ectoderm:

The outermost layer.
Develops into the skin, hair, nails, and the entire nervous system, including the brain and spinal cord.
Mesoderm:

The middle layer.
Forms structures such as muscles, bones, the circulatory system, kidneys, and reproductive organs.
Endoderm:

The innermost layer.
Gives rise to the lining of the digestive tract, respiratory system, and several organs such as the liver and pancreas.
These germ layers are fundamental to the formation of various organ systems and play a crucial role in the overall development of the organism.

Question 21

Trophoblast

Answer 21

The trophoblast is the outer layer of cells in the developing blastocyst, which forms around 5 to 6 days after fertilization.

It plays a crucial role in the implantation of the blastocyst into the uterine lining and contributes to the formation of the placenta.
The trophoblast differentiates into two layers: the cytotrophoblast (inner layer) and the syncytiotrophoblast (outer layer), which helps in nutrient exchange and hormone production to support the growing embryo.
It also facilitates the invasion of maternal tissues, allowing for the establishment of maternal-fetal circulation