Embryology Flashcards
MSK:
• Mesenchyme is the same as_____ ______ _______
embryonic connective tissue
MSK:
What is mesenchyme?
a loosely organized, mainly mesodermal embryonic tissue which develops into connective and skeletal tissues, including blood and lymph.
From the mesoderm
MSK:
The mesenchymal cells migrate and differentiate into what?
into many different types of primitive cell lines
MSK:
Examples of 3 different types of primitive cell lines?
- Fibroblasts (adult connective tissue forming cells)
- Chondroblasts (cartilage forming cells)
- Osteoblasts (bone forming cells)
MSK:
What does the mesenchyme in the paraxial mesoderm do?
it will transform into osteoblasts that will form the bony elements of the vertebral column
MSK:
What does the mesenchyme in the somatopleuric mesoderm do?
will transform into osteoblasts that will form the pelvic/pectoral girdles and also the bones of the upper and lower limbs
MSK:
What is the process of bone formation known as?
Ossification
MSK:
Whw does bone start to develop?
develops during the intra uterine life through 2 types of ossification
- Membranous type (intermembranous)
- Intra cartilgainous type (endochondral)
MSK:
What is intermembranous ossifiction?
(mesenchymal tissue will directly transform into bone) eg: the flat bones of the skull
MSK:
What is endochondral ossifiction?
(mesenchymal tissue first gives rise to a hyaline cartilage model of the bone, then the osteoblasts will convert that model into bone) eg: long and irregular bones
MSK:
What is the entire muscular system of the body developed from?
mesoderm
• The entire muscular system of the body develops from the mesoderm (except from the muscles of the_____, which develop from the _______ of the optic cups)
iris
ectoderm
The cardiac muscles of the heart develop from the _________ ______ surrounding the primitive heart tube
splanchnic mesoderm
The smooth muscles of the GI tract develop from the _______ _______ surrounding the gut tube
splanchnic mesoderm
MSK:
How many pharyngeal arches are there in the human development?
5
MSK:
Each pharyngeal arch has its own:
Cartilage skeleton,
muscular component,
sensory nerve supply,
motor nerve supply
MSK:
Muscles of mastication are dervied from which pharyngeal arch?
Which nerve is the muscle innervated by?
derived from the 1st pharyngeal arch and are therefore innervated by the Trigeminal nerve (V)
MSK:
Muscles of facial expression are dervied from which pharyngeal arch?
Which nerve is the muscle innervated by?
derived from the 2nd pharyngeal arch and therefore are innervated by the Facial nerve (VII)
Uro:
What are the 3 stages in the development of the kidney:
- Pronephros
- Mesonephros
- Metanephros
Uro:
Embryology of the kidney
Uro:
Embryology of Kidney
Uro:
Embryology of Kidney
Uro:
When doe the pronephros develope?
It develops during the 4th week of uterine life in the cervical region of the intermediate mesoderm
Uro:
What does pronephros contain?
The pronephros contains lots of segmental vesicles and has the pronephric duct that grows caudally toward the cloaca
- The pronephric duct is in the embryo and thus cannot filter materials outside the embryo.
- Therefore it is said that the pronephros kidney is non-functional in humans thus it degenerates.
Uro:
When is mesonephros developed?
- The Mesonephros kidney follows on from the development pronephros at around the end of the 4th week of uterine life
- It also comes from intermediate mesoderm and is located in the thoraco-lumbar area where the pronephric duct that was developed in the pronephros stage continue to elongated caudally and become the mesonephric tubules.
Uro:
Does the mesonephros degenerate?
Most of this tubules eventually degenerates but leave behind the Mesonephric duct or Wolffian duct which extends towards the cloaca
Uro:
The mesonephros is the functioning kidney during the __ trimester and it produces urine during weeks____
1st
6-10
Uro:
When does Metanephros develop?
This kidney begins to develop in the 5th week of the embryonic period and
appears in the sacral region of the intermediate mesoderm
Uro:
What happens to metanephros during the fifth week?
the mesonephric duct from the mesonephros kidney develops an outgrowth called the ureteric duct. This duct is close to the attachment of the cloaca.
The ureteric duct eventually forms the ureter, renal pelvis, major calyces, minor calyces and collecting tubules
- The ureteric bud interacts with a portion of undifferentiated intermediate mesoderm called the metanephric mesenchyme.
- This interaction induces differentiation and thus the formation of the renal tubules, glomerulus, loops of Henle, and the distal/proximal convoluted tubules
- If there is an abnormal interaction between the ureteric bud and the metanephric mesenchyme, several congenital malformation of the kidney may result.
Uro:
Embryology of the Kidney
Part A
Uro:
Embryology of the Kidney
Part B
Uro:
Embryology of the Kidney
Part C and D
Uro:
Embryology of the Kidney
Part E
Uro:
What is Sexual differentiation?
is the process of the development of the differences between males and females from an undifferentiated zygote.
Uro:
What carries the essential gene that determines testicular formation?
Y chromosome
Uro:
What induces differentiation of cells derived from the genital ridges into testes?
A gene in the sex-determining region of the short arm of the Y, known as SRY leads to the formation of testis determining factor (TDF), which binds to DNA and induces differentiation of cells derived from the genital ridges into testes
Uro:
When are the gonads distinguishable by?
weeks 6-8 of gestation.
Uro:
Uro:
Outline the embryology of testes
- Between the 3rd month and the end of pregnancy, the testes become transferred from the lumbar area into the future scrotum.
- This transfer is due to a combination of growth processes and hormonal influences.
- The gubernaculum testis arises in the course of the 7th week from the lower gubernaculum, after the mesonephros has atrophied. Cranially it has its origin at the testis and inserts in the region of the genital swelling (future scrotum).
- At the same time, at the inguinal canal along the lower gubernaculum, an evagination of the peritoneum arises, the vaginal process, on which the testes will slide through the inguinal canal.
Uro:
Embryology of the ovaries
Mesonephric duct (Wolffian duct) degenerates, small remnants may remain as epoophoron and paroophoron (in the mesentery of the ovary) and Gartner’s cyst’s (near vagina)
- Paramesonephric duct (Müllerian duct) grows and forms the oviduct (uterine horn) and the end opens into the peritoneal cavity and terminates in fimbria (finger-like extensions extending from the ovary)
- Away from the ovary, the two paramesonephric ducts fuse in the midline to form the uterus
- Cortical sex cords form after the primary sex cords degenerate and the mesothelium forms secondary cords
- The surrounding connective tissue differentiates to form follicle cells.
Uro:
Embryology of the uterus and vagina
The entire vagina is formed from the paramesonephric (Müllerian) duct and does not have a contribution from the urogenital endoderm
- The initially paired ducts fuse in the midline forming the single body of the uterus
- The ducts remain separate laterally where they form the uterine tubes (Fallopian tubes, uterine horns)
- The ducts peripheral attachment site to the urogenital sinus wall is described as the Müllerian tubercle
- The fused ducts also generate the vagina, under the influence of BMP4
- Oestrogen will also later alter the vaginal epithelium
What are the three germ layers?
Ectoderm, mesoderm and endoderm
Mesoderm splits into……
somatic mesoderm (next to endoderm) and splanchnic mesoderm (next to ectoderm)
three main body cavities will form in the space between…..
the two mesoderm’s
The three main body cavities are:
the pleural cavity,
pericardial cavity
the peritoneum
________ and _______ mesoderm become the two pleural layers (visceral and parietal respectively)
Splanchnic
somatic
Resp:
In what week does the laryngotracheal groove form?
week 4 of development
Resp:
What happens in week 4 of development?
- the laryngotracheal groove forms
- This gives rise to the trachea, bronchi and the tracheobronchial tree
- It then develops into the laryngotracheal diverticulum which by the end of week week 4 forms a globular respiratory bud
Resp:
• The respiratory bud then divides into 2 outpouchings called ____ ______ __
Primary bronchial buds
These buds continue to grow and secondary and tertiary bronchial buds develop
Resp:
What happens to the bronchial buds by the end of week 5?
By week 5, the bronchial buds have enlarged and their connections to the trachea form the main bronchi
Resp:
What happens after week 5? (lungs)
the lungs begin maturation
This continues up until the age of 8
Resp;
Lung maturation
Pseudoglandular stage is between how many weeks?
Resp;
Lung maturation
Canalicular stage is between how many weeks?
Canalicular stage 16-26 weeks